Things were great Saturday, Sunday, and most of Monday with no problems or glitches.
Then after playing Battlefield 2 Bad Company for a few hours last night the system just died mid game. Saturday and Sunday I had no issues playing a few hours each day.
After crashing, the pc does nothing 80% of the time when turned on. 20% of the time the cpu fan will start to spin and LED-1 of the MB APS flashes. The PSU fans never start. I've swapped out the PSU with a spare and it does the same. I've also removed the RAM and put them in one stick at a time, still no change. I've eliminated everything but the MB power connections. I also put a speaker on the MB and get no beeps.
The only OC'ing I was trying, was I raised the BCLK to 150mhz. Which I did Saturday and seemed to be working fine.
I haven't put a system together for a few years, but it was time for an upgrade. As far as OC'ing this was my first foray.
Might want to list out the rest of your specs as well, PSU especially. A bad PSU can cause all kinds of strange things.
It sounds to me that your CPU is overheating. The sudden shutdown is the computer trying to protect the CPU for bursting into flames. The reason the system doesn't usually turn on again when you try is that the CPU hadn't cooled off enough yet. However, I could be wrong. So, download Prime95 and RealTemp. Run them together for over an hour. Come back with the temperatures.
PSU is a generic 600W CompUSA PSU.
The PSU I put in as a test was a MadDog 450W.
I know neither are anything to mention, but they've worked well the last couple years.
Video wise, I have a ATI 4870.
I let it sit overnight and tried booting up this morning, with the same results.
When it first shut down, I opened the case and nothing seemed overheated.
I have Prime95, but didn't run it yet.