Whenever I open rhythmbox, it runs normally for a while (perhaps a few minutes) and then the screen becomes scrambled into small rectangular chunks (less than an inch wide and maybe a tenth of an inch tall). The chunks are various colors, and it does look as if random pixels were sampled from the previous display and blown up then returned to the screen in a slightly scattered way.
When I alt tab, elements move around on screen--the computer is responsive in some sense, but the screen stays scrambled.
Rhythmbox is the only program that does this to me. I'm running 12.04.
Where would I look to try and diagnose this?