Comment 3 for bug 796346

I've noticed this bug when using Ubuntu 11.04 (amd64) with classic GNOME desktop on two machines.
One machine has nVidia GTS graphics card (with proprietary drivers installed, still running 11.04), the other has Intel GMA graphics chip (but now it's upgraded to 11.10).

From time to time some random parts (don't matter if middle, edge or center, even the main menu part became affected) of top and bottom panels spontaneously became "transparent", so the desktop background became visible through these "holes".
The affected part "heals itself" by forcing it to redraw (covering it with other graphic object, switching to the other virtual terminal and returning back etc.).

Fortunately, I haven't noticed this strange bug in 11.10.