Alt+Tab and Alt+Enter Lag?

My specs:
i7 2600K @ 4.0 GHz
8GB G.Skill Ripjaws 1600 MHz
ASRock Extreme4 Gen3 Motherboard
ASUS DirectCU II 6950 2GB @ 890 MHz Core with Shaders Unlocked
Crucial M4 128GB SSD
Catalyst 11.8 Driver
Windows 7 64-Bit
900W Antec High Current PSU

So when I play games such as Modern Warfare 2 sometimes it would take me ages to alt+tab back into my game, sometimes I would even have to ctrl+alt+delete to make it move along just a little bit faster (doesn't always help). Basically I would tab out to check messages and then when I try to tab back in I would be facing a black screen for a long time. I recently tried alt+enter and just run it full screen but in "window" mode so I wouldn't have to alt+tab but it makes my game... stutter? It says my frames are at 60 and it feels that way except for the fact that it is kind of skippy.

This happened with my previous PC as well, I never did alt+enter with the old one but the same thing happens with the alt+tab.
My old GPU was a 5770. I'm thinking this is most likely a driver issue since there is no way my hardware would be breaking a sweat on any Call of Duty game or... League of Legends.

Edit: Don't have the alt+enter problem in Bad Company 2.