Vista Active screen is not responding to mouse

Since 2 days I have this problem after connecting the set: Labtec Ultra-flat Wireless USB (keyboard and mouse combination) Vista sometimes lose the focus of the active screen. This happens at random.For example, if I open IE7 and I open Word or notepad, I can no longer reamin within 1 of that screens .click on buttons or text (which is grayed out - in the sense of not running). The computer is not responding to these clicks. The mouse cursor (arrow) moves are just good with the movements. The wireless signal is therefore not disturb The strange thing is that I still click on the start button or the quick start toolbar icon. The same is also sometimes vice versa. The keyboard works in all cases still! I thought it was the mouse, so I have an old wired PS / 2 mouse connected. (together with the usb set). Both works if I move the cursor back and forth move. But, as vista is not responding to the USB mouse clicks of the mouse, it can not respond to the clicks of the PS / 2 mouse.
I therefore believe that it is not for the keyboard & mouse is only to Vista. Something it refuses to recognize that there is an active screen .... but what?

My cpu is neatly at 3 or 4%, the hard disk do not rattle. I do not know anymore. Does anyone have a suggestion?

I exactly had the same problem with a Targus USB wireless set. My "solution" Was ctrl-alt-del and start explorer process(succeed only when the 2nd click), then right again shut down explorer process and everything works again as it should.