Strange mouse click focus bug - desktop steals focus?

Hi!

I have a very strange bug, not so easy to explain.

Sometimes when I click on a window it will LOSE focus, and from that moment on every click will make any application lose focus.

The only way to give an application at least keyboard focus is to alt-tab to it, or otherwise activate it only by keyboard.

The moment there is a click anywhere, focus is lost.

On the desktop I can't click on the taskbar, it's like it doesn't get the focus neither, but I can click on icons on the desktop and can "bring up" that selection rectangle.

The only way I know of to get it back to normal (other than relogin or restart) is pressing ctrl+alt+del then click in that new "window" it brings up. It somehow makes the mouse "normal" again, then I can click cancel and continue work.

First experienced this problem on Sunday while playing with Windows Movie Maker. Back then the only method I knew was relogin, so I rather formatted hard drive and reinstalled Windows7 (professional), I was pretty shocked when realized it's still the same.

Couldn't tell what makes it appear, it comes while using different apps etc., seems pretty random.

I use a 2 monitor setup. Deactivating the 2nd monitor does not solve the problem, after it appeared.

Any ideas what may cause this? Video card failure maybe? I don't think it's the driver because the error reappeared BEFORE reinstalling the latest ATI drivers.

The only similar problem I could have found was a forum post from long long ago about similar problem in Windows XP, and there were no answers at all.

Thank you very much.