GTX560 /red green pixels+freez/

Hello, i have a very strange problem with my Geforce GTX560 (Asus ENGTX560 DC)

When i play CRYSIS 2 or when i run 3D MARK 11, at given moment the game (or the test) stop work.

First i see many Red ,Green and Blue flickering pixels and then everything Freeze! (and the only solution seems to
be restarting the system from the box button)

Here is my configuration, I will bi very thankful is someone help mi with my problem:

MB: ASROCK ALIVE NF5 E-Sata 2 (latest BIOS)
PSU: Corsair TX950W
CPU: AMD ATHLON x2 3600+ (clocked to 5000+ {2.4ghz}) (Everest test passed )
RAM: SUPER T CL2 DDR2 2.5GB (tested with memtest86)
WIN 7 ULTIMATE x64
SB: Creative Xtreme Audio
LAN: INTEL mt1000 pro
HDD: 2x Hitachi 80gb /240gb , 1x Western Digital Black Caviar 1TB
DVD, FLOPPY