Games enter windowed mode by themselves

The game will enter windowed mode without any user input at random intervals. I can be in the start-up menu not even touching my keyboard/mouse and the game will do this.

This is a very perplexing problem because I cannot find any information on the web.
The worst part is that not all games do this making it harder to diagnose.

Battlefield Bad Company 2 beta does this.
Company of Heroes Gold does it and Shattered Horizon does it. COD:MW2 does not, GTA 4 does not and Saints Row 2 do not.

Stuff running in the background:
Rivatuner
Fraps
Steam (for MW2 and shattered horizon)
Action center

GFX drivers: 196.62
Windows 7 Professional 64bit
GTX 275 @ 700/1512/1300
Intel E2200 @2.8GHz
Gigabyte DS3L
Onboard Realtek LAN and Audio
500GB WD Blue

I can post a dxdiag but is there an easy way to do it without taking up a ton of space?

Any ideas as to the cause?

Same problem here.
Updated all drivers and DirectX but to no avail.
GTA4, TF2, NFS SHIFT, L4D2, HL2, Hl2Ep1, HLEp2, Portal, MW2, Cod4 runs fine.

But Company of Heroes, Far Cry 2, and Battlefield Bad Company 2 runs in windowed mode everytime i run these games. When i tried to change the resolution to "fullscreen", the game freezes and later on crashed. No BSOD though.

Please fix this ASAP, any assistance would be deeply appreciated.
Thanks.