This may or may not help http://www.lvllord.de/?url=tools (but certainly won't do any harm!)
If you're using both LW's at the same time then the older one probably has a better connection & file information in the prefs folder & is hogging the bandwidth.

I've heard of issues from a few users using Windows Media Center who have reinstalled it or upgraded to it. Not sure why. It might be related to network settings. Also, did you make sure UPnP is enabled on WMC?

Do you see a brick wall in front of the blue world icon at the bottom of LW's interface?