I am running 1920*1080 and have not seen that - i am running a SVN version though - so maybe its already fixed!
Are you running the latest RC4 SVN version: 12-07-2008 10-44h - Revision:21026? I just updated to that one and I still have this issue. See screenshot attached, this time on a screen resolution of 1280x800. Anything but 1280x720 gives me this issue. Even 1920x1080 gives me this!
I have the latest SVN and don't see this issue either. Running 1080 resolution.
This is very strange. I have no idea what could be causing this since I don't have the issue on my other HTPC running RC3 at 1080i. I thought maybe it was an RC4 issue.
Anybody have any ideas whatsoever? How/why would this be happening?