Ati screen flicker problem

hello

i recently bought an ati sapphire 6870 ( since my last 6870 vapor-x broke )

and now, everytime I install the ati driver ( any version ) and start firefox/chrome/ET/LoL, I got screen flicker:





on the internet it says I should increase my 2D clock ( the idle clock of my gfx card is too low ) but even if I increase 2D+3D idle clock, whenever it goes down the screen flicker come back

I have win7 64bits ( already tried 32bits, win8 ), without driver there is no problem but I cant play =(


ps: I tought about sending back this crap gfx card and take a MSI GTX660 Gaming 2Go GDDR5 OC