I had a similar problem with Psi-Ops when I had an ATI X850XT.
I had to run ATI Tool to adjust Gamma in game as Psi-Ops was so dark on my monitor, this caused keyboard lag with it running. When I shutdown ATI Tool and loaded Psi-Ops the lag went away but the game was so dark I couldn't play it
Are you running any GFX util like ATI Tool for your 7600 card?