I THINK (hope) I have located the problem to be a bad memory stick. After reading a response to another post on this matter I tried booting with just one stick and it booted. Then two and it booted. Then three and it didn't. Then swapped out the third for the second and it did not. Swapped second back and it booted, so I apparenlty have a system with 4 gigs instead of six and some limited threading until I can hopefully replace that one stick.
Er, I hope..
I had a dx58so bios (ver.5200) working ok for almost a year, core i7 950, 4gb corsair, no overclock, heavy duty use for 3D renders during days. Then BF3 came and I decide to change my old gforce 9800 for an ATI 6770, at the begging everything was ok, after 2 week I started to get "POST atempt" failure during booting randomly, so I decide to upgrade my bios to the last version. Upgrade was ok, first boot I got 3 long beeps, no way to boot, so I decided to remove MB battery and wait an hour, it worked, and boot, but next boot, again 3 beeps, then repeaterd battery removal, and next boot go into bios and changed memory profile to XMB, big fail, the computer was self turing off during boot in a continuous loops, I got so angry was going to yell someone at INTEL support but could not find a phone number.
Then I decided to remove my ATI and go back to my geforce, everything is working ok now.
So there is something wrong with that board, and the voltage levels afecting memory performace when a powerfull video cards is installed. I dont think is a power supply problem, since the problem is happening in so many computers with good power supplies, am using a 800w Agiler. Intel should admit they have a problem and swap that board for something that works.