I am not sure where to put this. I'm guessing here since it's the only place that makes sense(somewhat) to me.
I am having an issue where I click in say a text box on a forum(happened here as i was trying to type this post). The little ' | ' line shows up and starts blinking as it usually does. But randomly, with out me clicking the mouse, or doing anything but typing, it goes away and the text box is no longer selected. I have to re-click on the text box in order to finish typing. When it does this, I get an error sound each time I press a key.
I suspect that it is this issue that is causing me to go to the desktop when I am playing a game in full screen.
That kind of sounds like a CTRL key may be stuck.
Have you tried using another keyboard?
Another thing you can try is, when that happens, hold down the CTRL key and then press left click on your mouse simultaneously.