desktop focus problem?

I have a triple monitor setup. I've noticed this problem off and on over the course of the previews and the release version.

What happens is I'm doing my normal Windows multitasking. But sometimes, the application Windows (let's say Notepad for example) appears stuck on the screen. I can't move the window around. I can't click on the exit button. None of my windows will respond. I can't click on a window in the background to bring it to the foreground. The only workaround is to minimize all windows (win+d) and then bring the window back up.

I'm noticed this on multiple systems actually. A laptop with nVidia graphics. A pair of desktops with 2 different generations of ATI/AMD graphics.

does anyone have an idea what's happening? changing graphics drivers didn't help.

Not sure to understand everything, how many GPU ( graphic card ) on the PCs you try it ?
I means are the 3 monitors connected to the same GPU ?

I don't experience any problem like this on my Eyefinity Xfire setup

maybe I shouldn't have mentioned the 3 monitor setup. because the problem has occurred on 3 different PCs, ranging from a laptop to 2 desktops, and from one screen to 3 screens.