Had been having problems posting to windows hosted blogs with wordpress via Windows Live Writer. Finally found the solution after googling for it. Apparently, its a security measure made to prevent attacks againt malformed HTTP status lines and headers. Not sure of the exact cause since only upgraded to Plesk 8.2 on the windows server but anyway, the solution works.
Added to live writer’s config file “WindowsLiveWriter.exe.config”
<?xml version =”1.0″?>
<httpWebRequest useUnsafeHeaderParsing=”true” />