2011 iMac 3.4 i7/6970M 1GB - Same problem after upgrading to Lion.
Looks exactly like the OP's attached picture, i can get it to reproduce the problem pretty easily by flicking the scrolling up and down very quickly on my magic mouse/trackpad.
Minimizing the window, and then recalling it back to the screen sometimes corrects it. Tried deleting the com.apple.finder cache, and plist and that didn't work. The thread on the apple discussion board had no answers either but had quite a few people with the same problem.
Hoping for a update soon, or workaround.