A while back, I posted some links to EPG data error reporting sites for Windows XP Media Center Edition (here and here). Recently, I have heard from a couple of folks who have had trouble reporting EPG issues for Windows Vista Media Center using these sites.
The Windows Media Center team is aware of these submission issues and is working on getting them fixed. In the meantime, you can use the forum at http://thegreenbutton.com/forums/90/ShowForum.aspx to report EPG data issues for Windows Vista Media Center.
If you use this forum, please make sure to use the template that is listed in the post pinned to the top of this forum (also located at this link - http://thegreenbutton.com/forums/thread/201523.aspx).