HD4870 512MB problem in games

Hello:
I have a problem with my Gainward HD4870 512MB in games. I play very often multi to Call Of Duty 4 and at explosions of grenades, I have some graphics bugs that appear as if there was a wave of ultrasound is a bit difficult to explain and so I believe think.Try to make a screen for you later.

Here is my setup
Intel Core 2 Duo E8500
RAM GSkill 2x2Go PC8500PK
Motherboard Asus P5Q-E
Graphics card Gainward HD4870 GS 512MB
Samsung SpinPoint Hard Drive 1000GB RAID version
Corsair TX-750W

Thank you in advance for your answers

what version of Catalyst? Currently there is the version 8.12 for 4800 series card. Updates display drivers from here

I did the latest version 8.12 but the same problem

Do you overclocked your card, if you've made the games become unstable, I have overclocked once and I had a blue screen for part of nfs carbon.

I also have problems with this card, more than 10 fps difference with the bench found the net in crysis (same resolution, the same options enabled)
(I have less points in sm2 and sm3 on 3Dmark 2006 with my 8800GT: s)
(E8200,4 Go de XMS2, HD4850 GS, Alim corsair). (E8200, 4GB XMS2, HD4850 GS, Alim corsair). I have to reinstall vista, because I had a 8800GT before and I thought of a software problem.You have tried reinstalling the games?
And you also this phenomenon in other games?

Yes in all other games too. I would do better to stay under Nvidia and the HD4870 has more than one fan thermo-regulated so it makes a noise not possible.