"Flickering problem"

Hello all,

I have some trouble with a "flickering" screen ie like green pixels lines appearing at different place varying with the background.

Parameters:
Config is 2 days old.
This happens when i'm at 120Hz 1920x1080 but not if i move down to 110Hz.
I had to flick the switch on the Card to get 120Hz.

Here is my config:
Intel Core i5-3570K (3.4 GHz)
ASRock Z77 Extreme4
Be Quiet ! Dark Rock Pro
Corsair Vengeance Low Profile 8 Go (2x 4 Go) DDR3 1600 MHz CL9 Crucial M4 128 Go
Seagate Barracuda 7200.14 SATA 6Gb/s 2 To
Samsung SH-222BB/BEBE
Corsair Carbide 500R
Seasonic X-660 80PLUS Gold
Iiyama 27" LED - ProLite G2773HS
Logitech Cordless Desktop MX 5500 Revolution
ASUS Radeon HD7970-DC2-3GD5

Regarding Software:
Catalyst 12.8
2D Pilot 8.01.01.1253
Direct 3D 9.14.10.0924
Open GL 6.14.10.11762

Thanks for your help