9800Pro Memory Problems

[d0l0t]

I was playing nfsMW and everything was ok, but when the race was finished there were TERRIBLE artifacts in the game-menu. :shrug: The video-memory started artifacting from that time on standard clock-speed (338). It worked well before and I even OC it a little.
I set the clock-speed down to 253 and it worked ok. That is why I realized that exactly the memory doesn't work correctly.
It is not because software: it artifacts even when Windows starts up.
My question is: how was the memory got out of order and how to fix
Sapphire 9800Pro r350 Hynix 2.5ns 256Mb 256bit

[Avg]

First set the clockspeed to default, then run a artifact scanner if there is still artifact make sure your hsf is working and making proper contact. If nothing does it make sure it isn't a driver problem by either uninstalling the driver or simply just booting into safe mode.

[d0l0t]

Thank you for your advices, but they haven't solved the problem.
It still does artifacts at default memory speed.
I reconnected the card, I uninstalled and then installed the drivers (tried new and older versions), but it didn't help.