Bad memory slot?

[TehSkelebones]

Hi all,

I have been having issues with my new PC for a few months and have been slowly ( as time permits ) eliminating hardware pieces as the problem.
The issue is:
While gaming at random intervals the PC will freeze with a low buzzing noise being emitted from the speakers, the keyboard is unresponsive and the system requires a hard boot to become responsive again.

The memory question:
I was using memtest86 (iso version) to test my memory (4 sticks of 2gb/1333 Corsair XMS3 ) typically memtest reported that the sticks were running at 565Mhz (or something similar) but one slot reports 365Mhz.
I emailed asus tech support and explained the same situation to them, I thought I would ask the community. To me this screams bad slot, RMA the board.

Your thoughts?

Asus M4a78t-E mobo
Phenom x2 555 (not oc'd)
8GB corsair XMS3 1333 RAM
Nvidia GTS-450
Ultra 750Watt psu
Seagate hard drives
Windows 7 pro 64bit

 

[mosox]

Most likely bad stick of RAM. Try with one stick at a time.

 

[TehSkelebones]

I thought that at first as well, one stick of RAM that I tested with memtest came back with errors, the system then rebooted. However that same stick of RAM when tested again in the same slot didn't give any errors. I am going to try running 6GB of RAM omit the potentially bad stick of RAM and slot and see what happens.