I just read an article with the following quote.
Update: Miguel Freitas, one of the xine project leaders, wrote to say:
Just a small update for your article: this week i added XvMC support toxine cvs based on Jack's patch.
It seems to work fine, however, several people have experiencingproblems with nvidia cards and high definition overlays (using XvMC ornot). the card gets into a bad state that only a reboot cycle can fix.nvidia engineers told us that their QA people do not stress test thedrivers with such huge images, so i guess this might get fixed on thenext release.