Weird issue with 4850 and 3dmark 1-3-5-6 and vantage

[Iraklis F.C.]

now there a puzzling problem for you guys , default sapphire 4850 crashes during all 3dmark bench sessions. That is a black screen or stripes across the screen...if i lower the memory freq from 993 to 970 the benchmarks will end succesfully....which i thought that could be because of faulty GDDR.

BUT furmark @ 1920X1200 stability test and games play fine at 993 memory freq (ie default clocks)

what the hell?

i tried with 8.6-8.7 and all hotfixes from futuremark installed