Mobo problem?

Hey all,
I bought a hp pavilon about a year ago, Has 2 gig, The mobo # is A8m2N-LA. At first I never had any problems with the pc until about a month ago. The pc would just turn off randomly and not turn back on for a couple of hours, so i suspected it was overheating. I replaced both fans and cleaned the inside of the case. It worked for about a day and started doing the same thing over again. Now the computer will not boot up at all, the fans and the lights come on. I replaced the power supply, still nothing, pulled all cards from the mobo, still nothing. I replaced the monitor, still nothing. (with video card and onboard video). I tried a diff. hard drive, and still nothing. Cleared the cmos and replaced battery. When i pull the memory out i do not get any beeps. Does this sound like a mobo issue? I'll try anything to get this working. I overpaid for this pc for it to sit there and look pretty.

Thanks in advance,
Derek