This didn't happen before today, and I also didn't have the problem after the first time I installed the DX11+HiRes update. When I first installed the updates it ran fine in fullscreen mode at 60Hz, I joined a game which was empty and left. Then at the multiplayer, I accidentally hit quit, quitting the whole game. I restarted the game, and now when I go to full windowed mode, it pushed my 60Hz to 24Hz and gives me major underscan. I also had this problem when I installed Crysis 1 on my computer. But this is the first time Crysis 2 has givien me this problem since launch.
Is there any fix? I'm using a XFX 5870. Everything is set to extreme and DX11/HiRes pack are turned on.
I also used the "demo" command before I hit quit, does that have anything to do with the problem? I did also delete the "system.cgf" file. . .
UPDATE!
HOW TO FIX:
Run the game and go to option > Graphics, then go on "Full Screen" change it to NO.
Restart the game and make sure DX11 is enabled (If you want DX11).
Now, as soon as the game starts and you see the creepy (but cool looking) Cryengine Logo/eye hit ALT + Enter! The games resolution will change to 1600x1200 @60Hz and then 1920x1080 @ 60Hz. This is the only fix I've found to the problem.
Please keep bumping the thread every hour or so, so someone from Crytek sees this.