Overclock (if you can call it that) causing a problem?? Help!

Hopefully somebody can give me some suggestions on what is wrong here - sorry for the long post, but
I didn't want to miss anything.

My system is an older rig that I've had the cpu, memory and gru overclocked on from time to time.
Recently I've been running the cpu at stock (2.6Mhz)), overclocking just the gpu core (614Mhz) and running
the memory at 2-3-2-5 1T at 2.7V (the memory is rated for 2.5-3-2-5 with no mention of command rate).

Any way, yesterday when I powered on the system, initially it didn't even post. Power came up, fans spun, but never got the bios splash screen, etc.. I hit the reset - everything came up. I didn't give it a second thought.

Today the same thing happened. But this thime after the reset, it didn't boot into windows. When I hit the reset again, nothing happened. I had to flick the power switch on the PSU to shut off all power to power it down. Then, as soon as I hit the switch again, it came right back on - typically I would have to hit the chassis power button before it would start up. As it booted into BIOS, I got an error saying 'overclocked failed - hit F1..etc.". So I went into BIOS, check all my settings - nothing had changed. So I exited out without changing anything. The system the proceed to boot up into windows. It ran for a short time and then froze on me while I was doing almost nothing.

So another reset - which didn't take. Had to power down with the PSU switch again - and when I turned it back on I got the same weird 'auto' start. Basically went though the same steps again above just to see if it would happen again - and had the exact same results.

So after powering down again at the PSU, I also pulled the plug so I could change RAM. I happened to have two extra 1G sticks of Cosair 2-3-2-5 DDR 400 so I swapped them with my Ocz - ran the same tests - and had almost the same results. This time after booting up into windows, I was able to work for a while (simple 2D apps) - but eventually it locked up again. So I'm thinking it probably not memory as the Cosair stuff has never been used.

So this time after the PSU power switch and power up, I went into BIOS and changed the memory timing to 'auto' and changed the DDR voltage to auto as well. The system booted up into Windows and has been running stable now for about an hour (not doing anything stressing to it at the moment - I'm in the process of backing up my HD!!!). When I check cpuz, I see the ram settings are at 3-3-3-8 2T 2.5V (higher then what the memory is rated for, but that appears to be the settings in SPD as well).

At any rate, any thoughts on what the issue could be. I thought initially maybe memory but swapping out the rams sticks didn't seem to make a difference until I set the timings to 'auto' - and both sticks where rated for the same speed.

The mobo is old -and refurbished (new caps) at that - so I'm thinking maybe its on the way out? The weird 'auto' on when turning on the PSU would seem to point to the mobo as well (I did check the PSU 12V and 5V rails with a multimeter and they seem quite stable and exactly where they should be). I don't see any bulging caps or anything on the card - but the last one I had that went didn't show that either.

I suppose I can slowing start changing the RAM settings again and see what happens, but I'm not sure what that will prove.

Any thoughts on what it could be or how to narrow this down further?

Thx for any help!
Sdrac

Evilonigiri -
Thanks for the suggestion. I have Orthos so I'll try that as soon as my backup is finished. I'll post back when I have the results.

Sdrac