Well, I was recently playing Nexuiz and my mouse was a bit.. tipsy. It kind of skipped around and whatnot and the mouse was fine.

I thought, oh well.. Nexuiz is a bit messed up on my system.

Later on I got darkplaces for Quake and it's doing it on that too.

It seems like when I turn it.. Well, I'll record a video soon.

Gentoo Linux 2.6.17, AMD64, GeForce 6600GT.

Seems to be directly related to Vsync, and I love my Vsync

Does gl_finish 1 in the console help? You can open the console with shift-escape.. If not i guess its best to set it back to 0 then.