I also would like to report tearing when playing video. So frames get desynchronized, but this is general problem. It might have something to do with thread timing and 64 bit kernel. It doesn't happen too often. But happens also with lower quality videos.
I have already discussed this topic in Ubuntu forums, and they suspect problem isn't directly related to VLC.
Ubuntu 64 bit 7.10, Nvidia 7600GT, Xvideo, vblank sync enabled, VLC 0.8.6c (64 bit)
Update:
This seems to help: nvidia-settings --load-config-only
I didn't know that I need to run that command after very X restart.