I've had nothing but trouble over the years with my wife's Shuttle computer. It was running fine for a year or so now, after replacing the PSU, but now it's doing another odd thing.

I'm attempting to simply set up a fresh OS install, but the computer is shutting down. At the moment, I can keep it turned on for about 3 minutes, then it just shuts off (almost the opposite of the problem I was having before!).

I don't even have to be doing anything to have this happen. The last couple times, I just went into the BIOS, waited, and eventually it just shut off. Those times, I watched the CPU temps to see if they were slowly building too high. Correct me if I'm wrong, but 56 degrees isn't outrageous for a Shuttle, right? It seemed to waver between about 54 and 59, mostly staying on 56.

To further clarify, when the computer shuts down, it doesn't let me turn it back on. There's a red light on the motherboard, and no matter how often I press the power button, it won't let me turn it on again. The only way to turn it on again is by unplugging the power cable, or by holding the power button down until the red light shuts off and then pressing the power button again.

Any thoughts? What might be failing?