I don't have exact STR, but basically I was bringing a window up that had two tabs. 1) Open window with two tabs 2) minimize 3) hover over fx icon on taskbar 4) hover over thumbnail 5) click on thumbnail to activate tab I've never seen this before, so seems like it might be a recent regression.

Seems like this could be related to some of the gradient cache work that's happening in bug 800319

(In reply to Jeff Muizelaar [:jrmuizel] from comment #1) > Seems like this could be related to some of the gradient cache work that's > happening in bug 800319 That's exactly what I was thinking.

Just got this again, str: 1) browser with four tabs, the browser was in the background 2) hover over taskbar to bring up tab thumbnails 3) click on a thumbnail

navigating in a new tab gave me this.

The fix to bug 800319 recently landed, so we should check with that in. Also I'm pretty sure tab thumbnails are off by default so we should probably mention that in the STR :).