I get that problem as well, after playing games, and bizarrely enough when AOL explorer runs. By the looks of things, it may have something to do with apps making DirectX calls to draw on screen that is messing things up for WB (video -> DirectX, games -> DirectX 3D, AOL browser (non-standard GUI + tab preview overlay) -> DirectX, anyone see the pattern?) My card is a 5900XT.