Actual Gamma stuck at setting '1' - JENS TAKE A LOOK PLEASE

[plees]

1. Windows Ultimate 64-bit

2. Desktop PC

The problem is as following: Even though i run the gamma "bar" up and down, the actual gamma of the game, is as if it was stuck at 1.
Example: I move the bar to a gamma value of 2.0, then the screen becomes as bright as if the value was 2.0 for half a sec, then quickly switches back to a dark screen, with the gamma equal to the value of 1.0, however the "bar" is still at 2.0.

I can change EVERY other setting of the game, it is only the gamma value that is unchangable.

I have tried running full screen and window mode, none of them make a difference.

My GFX card is an nVidia GTX 560