5850 and 6850 together, 6850 slows down

[malevolent]

Hi,

Im having a problem with 5850 and  6850. Just installed them properly, 5850 @ 900MHz, 6850 @ 850, both running guiminer (phoenix), 5850 was 350Mhash/s and 6850 was at 220Mhash/s, but after about 2h, 6850 slowed down to 80Mhash/s, without flags its even worse (65mhash/s). I cant get it to return to its full speed.
OS - win7 pro 64
psu corsair vx550
asus p5q-e
gpu driver ver. 11.5

temps are below 80C
if I stop minig with 5850, 6850 is still working at 80mhash/s. Why did work fine for only 2h? :>

Any help is appreciated, if any more details are required I'll post them in ca. 10h.

[1715568686]

1715568686

[1715568686]

1715568686

[BinaryMage]

What's your GPU usage percent on the 6850? It should be at nearly 100% if all settings are correct.

[Lightspeed]

is the clock speed still @ what it should be?

[malevolent]

After it slowed down, the gpu usage fell to around 50%. An hour after my post I got a BSOD, there was a problem with some ati file.
BUT I think I solved my problem: moved back my HD 5850, it's now running @ 805 Mhz, 12h uptime so far.

EDIT: just tried to overclock my 5850 a bit more, only by another 20 MHz... got a BSOD after 10 min. So I think 805 is max stable I can get.
Didn't increase any voltages so far - my temps are from mid 70s to mid 80s, after adding 5850, my 6850 is almost 15C hotter ;]