The problem with pasting information from other locations is the interpretation of the formatting. Windows Live Writer is going to try to paste the information as accurately as possible, but issues with the translation or the theme can be an issue. You may want to try pasting the information without the formatting [EDIT>Special Paste].
OR
I think you should try CLIPBOARD LIVE. http://gallery.live.com/liveItemDetail.aspx?li=326740b7-413b-4e0a-bf51-dd49258fd84a&bt=9&pl=8
This has some options for when you copy and paste information. Don't forget to check the options for the plug-in. It's very useful.