I tried to use WLW to post to my blog, running Quills on Plone 2.5.5/Zope 2.9.6.
However, this seems not to be as easy as I though. I figured, that WLW makes a POST to my blog, but get's a 401 as the answer - in order to post XML-RPCs there has to be a basic auth header present, which doesn't seem to be there ... at least that's what Fiddler is telling me.
Is it possible for you to send me a fiddler trace? Make sure you change your password to a temp password before sending it so I don't see your real password.