Maximum PC

Hi,

My system is an i5-3570k @ 4.2ghz (sync turbo ratio setting only.Everything else is default setting.)
Asus p8z77-v lk
16gb Geil Evo veloce 1600 (4x4gb)
2x xfx radeon 6870 (925/1100)
Corsair tx750
OCZ vertex plus R2
1tb HDD
x-fi sound card
Antec Kuhler 620

When I run the ram at 1333 I pass 12hours prime95 blend test with 0 errors.

When I run in XMP mode I get 1 error in worker #3 at the 8hour mark. I have the most update bios and the error was hardware failure. In the bios before the current one I got 1 error in 2 of the 4 workers, but they were rounding errors. I have tried manually setting the ram to 1600 and that was 1 rounding error in 2 of 4 workers as well.

I ran memtest86+ (usb) in xmp mode for 15hours with 0 errors.

I have also ran Intel burn test, very high, in XMP with 0 issues.

What could the problem be?

CPU max temps were 68,70,71,68 during prime95 blend.