New build instability (Z77 Extreme4)

[yannis76]

Hi,

I changed my mobo from P67 Extreme4 to Z77 Extreme4 with a clean installation of Windows, but the system seems quite unstable.
The 1st problem was I could not restart the system without entering the bios, but that was corrected with a CLR CMOS. Now random lockups and restarts happen while browsing and sleep modes dont seem to work all the time. Furthermore I have noticed some artifacts in one game. My gpu temp is reaching 83oC with Furmark and memtest doesnt show any error.
These is somthing wrong in the system, but I dont know where and what to check first. Any help?

thx
Yannis
(I have posted this also in Motherboards section)