After assembling new PC on GA-EP45-UD3R motherboard and Corsair 2x2GB 8500C5D memory everything was fine for a couple of days. Then I got the "Memory Testing..." screen during the boot and then constant restart. The only change i made in BIOS was DIMM voltage set to 2.1v. To get into BIOS I had to switch the PSU off and wait a little.

The PC failed after I moved the box to another building - I am still not sure if that is the case. After I brought it back home - no problems at all at any BIOS settings. I can't even replicate the situation with the "Memory Testing...."

So I did memtest+ for 1 hour on 2x2gb dimms. Replaced the dimms, used other banks. Everything works.

Same failure occurred again. I could not find any problem at home so brought the box back and it ran fine from the first boot. Tried several restarts and shut-downs - no problem. Next morning they got the same "Memory Testing..." screen during the boot and reboot loop. Replacing surge protector did not help.

The only way to start the PC after the failure is to unplug or shut the PSU off.

Now I am on the phone with them and it looks like external hard drive can cause the problem. They have Seagate FreeAgent Pro connected via USB.

Please advise.