Specs

CPU - AMD Opteron Dual core 165
RAM - Corsair XMS4400PRO 2G - 1Gx2
PSU - Ultra XFinity 600w
HSF - Thermaltake Big Typhoon
HDD - WD 74G Raptor
Mobo - DFI Infinity
GPU -- eVga 7600 GT

Everything worked fine with no issues and with a mild 2.44Ghz OC For 1 week.
Folding 24/7, gaming, and daily use.

Problem - Came home to find the PC powered down and it would not boot.
HSF spins for 3 sec then stops. Mobo LED lights up & stays lit.
RAM LEDs light up but go out with the HSF.

Trouble shooting.

Check all cable connections. All OK. No boot.
Remove DVD RW and un needed Hard drives. No Boot
Change RAM to OCZ 4200 Platinum. No Boot.
Swap Opty165 with Known working AMD 3500+. No Boot
Put Opty165 in Biostar Mobo from the socket just vacated by the 3500+. SCORE BOOT first time.

Looks like a RMA for a DFI Infinity that is not even 3 weeks old yet.

This does not make me happy as now the 3500 will be out of folding commission until I can get the RMA Mobo replacement.

This has been a public service announcement brought to you by a disgruntled geek.

Try testing the PSU, just the PSU and a couple of fans connected to it.

http://modtown.co.uk/?psumod

BUMP / Update

Thanks for the PSU tip feral. But alas it was not the PSU.

You are right I should have checked the PSU before just assuming the mobo was the problem.
Another thing was the RAM. I did not test that at the time I made a good calculated guess.

Before just dumping $$$ into the mobo I did go back and test the PSU and RAM in
other rigs.

My Opty 165 now resides comfortably in a DFI LP UT NF4 Ultra D.

The DFI Infinity did not last very long only 1 week. I hope the replacement does better.

I like the Ultrad D and can only hope that it will server as well as my DFI LPty NF4 SLI DR.

Never the less dfi rocks. Now I'll be taking off to OC that badBOY.

Glad to see things are working as they should now.