Mysterious shutdown

Hi, I've recently experience mysterious shutdown on my AMD64 system. Just now, after the computer had been on, playing music (the only thing being done on it), it suddenly shut itself off. I have to "unplug and replug" the powersupply to have the computer start again. Is it possible, that some "hardware" in the system is causing this, the memory in the computer are two brand new ... two kingston 512Mb modules, the hard disk is also new, a SATA one. The CPU was bough earlier this year, the system being run is SuSE 9.2, with the latest upgrades from apt4rpm (gwdg.de). Personally, I'm thinking "powersupply" ... has anyone run into this behaviour? Örn