i'm getting increasingly severe corruption problems in finder windows as well. i've got a new imac 27" with two 27" displays.
i installed lion and started experiencing numerous video corruption problems in the finder.
windows in the finder start experiencing color shifting... and now there's an odd pixelation of window bordering going on.
there seems to be some correlation with whether or not i'm running chicken of the vnc, or alternatively apple remote desktop, but i haven't convinced myself of that, as that the only thing that seems to solve the corruption issues is a restart.
when i next get the chance to restart, i'll not launch either of the remote apps, and give it a day or two and see if the corruption occurs when neither of those two apps are running.