Yesterday I finished changing the Windows Live Writer Plug-in which will help you to update your twitter status when ever you post from your Windows Live Writer. The earlier versions where using the username and password to authenticate twitter (Twitter blocked this method now), while the latest version 1.1.0 uses Twitter oAuth.
The plug-in is approved and available in the Windows Live Gallery you can get the plug-in from here. If you want to read more about the Twitter Update Plug-in for Windows Live writer read this Twitter Update Plug-in for Windows Live Writer using oAuth