It is already updated. I had F5 version, and updated it to F7. That was the first thing came into my mind.
CPU: i5-2500K
FAN: Cooler Master Hyper 212 Evo
RAM: Hynix DDR3 1333, 12GB
GPU: Sapphire Radeon HD 6770 1GB GDDR5
HDD: Samsung 1TB, Seagate 2TB
DVD: Pioneer 212D
PSU: Chieftec 650W
Actually, it was the upgrade. I was replacing CPU and MB (had AMD before). All that hardware perfectly worked without any problems with MB on 785 AMD chipset. MB had pcie 2.0 x16 slot.
Also, I tried to reinsert the CPU, cause on russian forum I've found that such kind of behaviour can be caused by bad CPU socket (not pciex). However, that didn't help.
Currently GPU installed on the second slot and works fine. Onboard (CPU) GPU works without any problems as well.