Well...
I
1 overwrote all the files on xmlrpc
2 made a new account on WLW, Joomla(a superadmin) and Zoundry
3 my collation is utf8_general_ci, even if there are some tables (related to 3rd parties components) on latin1_swedish_ci
Situation is:
I can post new topics on both editors
I can't see old articles on WLW (and remember that I could 3 days ago?)and I don't even know if it possible with Zoundry...
I can post you the new WLW log...

Code:

WindowsLiveWriter,528,None,00014,27-apr-2008 00.25.46.765,\"DisplayableException occurred: WindowsLive.Writer.Extensibility.BlogClient.BlogClientInvalidServerRes ponseException: Risposta del server non valida - La risposta al metodo metaWeblog.getRecentPosts ricevuta dal server del blog non era valida: Invalid response document returned from XmlRpc server at WindowsLive.Writer.BlogClient.Clients.XmlRpcBlogClient.CallMethod(Stri ng methodName, XmlRpcValue[] parameters) at WindowsLive.Writer.BlogClient.Clients.MetaweblogClient.GetRecentPosts( String blogId, Int32 maxPosts, Boolean includeCategories) at WindowsLive.Writer.BlogClient.Blog.GetRecentPosts(Int32 maxPosts, Boolean includeCategories) at WindowsLive.Writer.PostEditor.RemoteWeblogBlogPostSource.GetPosts(Rece ntPostRequest request, Boolean getPages) at WindowsLive.Writer.PostEditor.RemoteWeblogBlogPostSource.GetRecentPost s(RecentPostRequest request) at WindowsLive.Writer.PostEditor.OpenPost.BlogPostListBox.GetRecentPostsA syncOperation.DoWork() at WindowsLive.Writer.CoreServices.AsyncOperation.InternalStart()\",\"\" WindowsLiveWriter,528,None,00015,27-apr-2008 00.30.57.125,\"Failed to download template Framed: System.Exception: Unable to locate blog post elements using most recent post at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous) at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args) at WindowsLive.Writer.BlogClient.Detection.BlogEditingTemplateDetector.Pa rseWebpageIntoEditingTemplate_OnUIThread(Control uiContext, BlogPostRegionLocatorStrategy regionLocator, IProgressHost progress) at WindowsLive.Writer.BlogClient.Detection.BlogEditingTemplateDetector.Ge tBlogTemplateFiles(IProgressHost progress, BlogPostRegionLocatorStrategy regionLocatorStrategy, BlogEditingTemplateStrategy[] templateStrategies, BlogEditingTemplateType[] templateTypes)\",\"\" WindowsLiveWriter,528,None,00016,27-apr-2008 00.30.59.531,\"Failed to download template Webpage: System.Exception: Unable to locate blog post elements using most recent post at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous) at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args) at WindowsLive.Writer.BlogClient.Detection.BlogEditingTemplateDetector.Pa rseWebpageIntoEditingTemplate_OnUIThread(Control uiContext, BlogPostRegionLocatorStrategy regionLocator, IProgressHost progress) at WindowsLive.Writer.BlogClient.Detection.BlogEditingTemplateDetector.Ge tBlogTemplateFiles(IProgressHost progress, BlogPostRegionLocatorStrategy regionLocatorStrategy, BlogEditingTemplateStrategy[] templateStrategies, BlogEditingTemplateType[] templateTypes)\",\"\" WindowsLiveWriter,528,None,00017,27-apr-2008 00.31.19.953,\"Exception parsing XML-RPC response: WindowsLive.Writer.CoreServices.XmlRpcClientInvalidResponseException: Invalid response document returned from XmlRpc server ---> System.Xml.XmlException: '', hexadecimal value 0x1C, is an invalid character. Line 71, position 28. at System.Xml.XmlTextReaderImpl.Throw(Exception e) at System.Xml.XmlTextReaderImpl.Throw(String res, String[] args) at System.Xml.XmlTextReaderImpl.ThrowInvalidChar(Int32 pos, Char invChar) at System.Xml.XmlTextReaderImpl.ParseText(Int32& startPos, Int32& endPos, Int32& outOrChars) at System.Xml.XmlTextReaderImpl.ParseText() at System.Xml.XmlTextReaderImpl.ParseElementContent() at System.Xml.XmlTextReaderImpl.Read() at System.Xml.XmlLoader.LoadNode(Boolean skipOverWhitespace) at System.Xml.XmlLoader.LoadDocSequence(XmlDocument parentDoc) at System.Xml.XmlLoader.Load(XmlDocument doc, XmlReader reader, Boolean preserveWhitespace) at System.Xml.XmlDocument.Load(XmlReader reader) at System.Xml.XmlDocument.LoadXml(String xml) at WindowsLive.Writer.CoreServices.XmlRpcMethodResponse..ctor(String responseText) --- End of inner exception stack trace --- at WindowsLive.Writer.CoreServices.XmlRpcMethodResponse..ctor(String responseText) at WindowsLive.Writer.CoreServices.XmlRpcClient.CallMethod(String methodName, XmlRpcValue[] parameters) <?xml version=\"\"1.0\"\"?> <methodResponse> <params> <param> <value><array> <data> <value><struct> <member><name>userid</name> <value><string>62</string></value> </member> <member><name>dateCreated</name> <value><dateTime.iso8601>20071011T17:35:02</dateTime.iso8601></value> </member> <member><name>postid</name> <value><string>30</string></value> </member> <member><name>description</name> <value><string>&lt;p&gt; Dagli Stati Uniti abbiamo recentemente importato un nuovo termine: &amp;ldquo;subprime&amp;rdquo;. Questa parola &amp;egrave;&amp;nbsp; collegata a &amp;ldquo;crisi&amp;rdquo; e &amp;ldquo;mutui&amp;rdquo;. Crisi dei mutui subprime &amp;egrave; una delle cause pi&amp;ugrave; dirette dei recenti tonfi delle Borse internazionali e del rallentamento delle economie collegate a quella americana, come&amp;nbsp; quella Europea e di conseguenza italiana. In alcuni stati americani, questa crisi ha trasformato interi quartieri popolari e residenziali in territori simili ad un far west. A causa dell&amp;#39;aumento dei tassi d&amp;#39;interesse, decine di migliaia di famiglie hanno dovuto svendere a prezzi bassissimi le loro case poich&amp;eacute; i loro mutui, concessi con troppa facilit&amp;agrave;, sono aumentati anche dell&amp;#39;80%.&lt;/p&gt;</string></value> </member> <member><name>title</name> <value><string>Mutui onerosi? Cambia mutuo</string></value> </member> <member><name>link</name> <value><string>http://www.galleryimmobiliare.it/content/view/30/</ string></value> </member> <member><name>permaLink</name> <value><string>http://www.galleryimmobiliare.it/content/view/30/</ string></value> </member> <member><name>mt_excerpt</name> <value><string></string></value> </member> <member><name>mt_text_more</name> <value><string>In Italia nulla di tutto ci&amp;ograve; &amp;egrave; all&amp;#39;orizzonte, ma l&amp;#39;aumento dei tassi, associato ad aumenti delle rate dei mutui, ha messo in difficolt&amp;agrave; le famiglie che li avevano in precedenza contratti e soprattutto ha reso pi&amp;ugrave; riflessivi i nuovi compratori. Ne deriva un rallentamento generalizzato per quanto riguarda la velocit&amp;agrave; di circolazione delle propriet&amp;agrave; immobiliari e di conseguenza un diffuso ribasso dei prezzi, pur tra tante eccezioni. Se fino a uno o due anni fa il tempo medio per completare una compravendita era di tre/sei mesi, ora i tempi sono quasi raddoppiati. L&amp;#39;aumento dei prezzi si &amp;egrave; bloccato e questi sono regrediti dal 5% al 20%. La nuova tendenza del mercato permette oggi, a chi ha un mutuo troppo oneroso, l&amp;#39;azzeramento o l&amp;#39;abbattimento di una grossa quota della penale per estinzione anticipata e la rinegoziazione dello stesso a condizioni pi&amp;ugrave; favorevoli. Da quest&amp;#39;anno infatti, i decreti del Governo relativi all&amp;#39;ampio capitolo delle liberalizzazioni, hanno per legge abolito la penale, regalando ai cittadini questa opportunit&amp;agrave;. Consultando il proprio consulente di fiducia c&amp;#39;&amp;egrave; la possibilit&amp;agrave; di usufruire al meglio di questa occasione. &lt;p&gt;Antonio De Paolo&lt;br /&gt;Presidente Provinciale Fiaip&lt;/p&gt;</string></value> </member> <member><name>mt_allow_comments</name> <value><int>1</int></value> </member> <member><name>mt_allow_pings</name> <value><int>0</int></value> </member> <member><name>mt_convert_breaks</name> <value><string></string></value> </member> <member><name>mt_keywords</name> <value><string></string></value> </member> </struct></value> </data> </array></value> </param> </params> </methodResponse>\",\"\" WindowsLiveWriter,528,None,00018,27-apr-2008 00.31.19.953,\"DisplayableException occurred: WindowsLive.Writer.Extensibility.BlogClient.BlogClientInvalidServerRes ponseException: Risposta del server non valida - La risposta al metodo metaWeblog.getRecentPosts ricevuta dal server del blog non era valida: Invalid response document returned from XmlRpc server at WindowsLive.Writer.BlogClient.Clients.XmlRpcBlogClient.CallMethod(Stri ng methodName, XmlRpcValue[] parameters) at WindowsLive.Writer.BlogClient.Clients.MetaweblogClient.GetRecentPosts( String blogId, Int32 maxPosts, Boolean includeCategories) at WindowsLive.Writer.BlogClient.Blog.GetRecentPosts(Int32 maxPosts, Boolean includeCategories) at WindowsLive.Writer.PostEditor.RemoteWeblogBlogPostSource.GetPosts(Rece ntPostRequest request, Boolean getPages) at WindowsLive.Writer.PostEditor.RemoteWeblogBlogPostSource.GetRecentPost s(RecentPostRequest request) at WindowsLive.Writer.PostEditor.OpenPost.BlogPostListBox.GetRecentPostsA syncOperation.DoWork() at WindowsLive.Writer.CoreServices.AsyncOperation.InternalStart()\",\"\"

Thank you very much,
Guido

Thank you for send.

I seem to have returned a correct response. However, a wrong character-code seems to be included.

QUOTE:
hexadecimal value 0x1C, is an invalid character. Line 71, position 28.

The error went out when testing to return the response log that you sent.
The character that doesn't exist in the article in UTF-8 is included or there seems correctly to be a character that is not UTF-8.
Please correct a past article.

It seems that it is because different character encode exists together.

Thanks

Now it works, but don't know why, since the only thing I did has been:
1 erase the last article I've posted through WLW
2 paste the same exact html content in a new article with same title

On another pc, with another joomla account, WLW didn't allow to post new articles even after the first WLW worked correctly,
so I recreated an account with the same data, and now it can post...

Not exactly a reassuring behaviour, isn't it?

Please, let me know how I could mess with utf-8 if db and clients are all set on utf-8

I do not understand the reason either, but give an example in Japanese Joomla!.

1. All Joomla! files are stored in UTF-8 no BOM.

2. Setting of PHP is as follows.

default_charset UTF-8
mbstring.language neutral
mbstring.internal_encoding UTF-8
mbstring.encoding_translation Off
mbstring.http_input auto
mbstring.http_output pass

3. All databases are UTF-8.　

But there may be the case that a problem happens if you make it these settings.

Please send PHP setting of your mbstring and iconv.

Thanks.

Joomler, thanks again for your patience, I've waited so long because I wanted to monitor more precisely the bahaviour of the system.
It revealed to be very strange: sometimes it work without problems, then stops giving errors, and it resumes without touching anything.
I've checked my PHP settings, and they aren't like yours...I know this should be an issue, but I'm on a shared hosting, and don't believe they are going to change settings...
What do you advise me to do?

ICONV
iconv support enabled
iconv implementation glibc
iconv library version 2.3.4

Directive Local Value Master Value
iconv.input_encoding ISO-8859-1 ISO-8859-1
iconv.internal_encoding ISO-8859-1 ISO-8859-1
iconv.output_encoding ISO-8859-1 ISO-8859-1

MBSTRING
Multibyte Support enabled
Japanese support enabled
Simplified chinese support enabled
Traditional chinese support enabled
Korean support enabled
Russian support enabled
Multibyte (japanese) regex support enabled

mbstring extension makes use of \"streamable kanji code filter and converter\", which is distributed under the GNU Lesser General Public License version 2.1.

Directive Local Value Master Value
mbstring.detect_order no value no value
mbstring.encoding_translation Off Off
mbstring.func_overload 0 0
mbstring.http_input pass pass
mbstring.http_output pass pass
mbstring.internal_encoding ISO-8859-1 no value
mbstring.language neutral neutral
mbstring.substitute_character no value no value

Please send a title and the contents of the article when an error happened by an email.

I test it.

Thank you!