random annoying issue
 

When playing My window will randomly drop out of full screen into a desktop window ( as alt-enter does )
Any ideas on why its doing this? It can happen once a day or every 5 minutes.

First off the top guess is your keyboard is having keys issue. Other than that, perhaps a program is stealing focus and screwing up your full screen mode. Try going through task manager and killing all apps you don't recognize and try to run the game, and see if it fixes the issue.

That's all that comes to mind as possible reasons.

..
 

Nothing new on taskbar, and it does it even when I am not using the keyboard. It also does it if I am playing AoE3 or the like. so guessing its a windows issue. Roaming their boards next. tnx )

not all apps will appear on your task bar. I meant press CTRL+ALT+DEL and look at the process list, killing random stuff that looks strange (googling each one can give you hints what it's about).

Most likely an app is ninja stealing focus in one way or another.