I wonder if this is an NV bug. If it is, it's also an ATI bug (at least for older drivers.) It occurs on both my Ubuntu boxes, one of which is a four year old Lenovo Z61M running Ubuntu 10.10 with ATI x1400 video, the other is a newer Dell T3400 running 10.04 with an NVidia Quadro FX 750. I'm also running Compiz on both machines.
I will double check when I get home tonight to make sure I'm not confused about the laptop!