It seems that when I open a tool (one that has a dialog box) and then click inside the drawing area, the dialog box fails to render properly. I've attached a screenshot of this phenomenon with the mirror tool, but I've seen it with several other tools.

Any ideas?
(Before anyone asks, I'm running 2GB DDR400 RAM, AMD Athlon 64 2.4gHz processor, GeForce 7900GT graphics, and all my drivers are up to date.)