Yes, it could be due to poor/inconsistent power in the mains. But this is rare, and usually doesn't affect the computer. But has been known to happen. Hopefully that fixed the problem!

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AMD Athlon 64 X2 4400+ (@2.6 GHz)
2x1GB OCZ Spec. Ops. PC3200
ASRock Dual939-SATA2
Antec TruePower 550 watt PSU
80 GB Seagate Barracuda SATA 7200 rpm
300 GB Seagate Barracuda SATA 7200 rpm
120 GB Maxtor ATA/133 7200 rpm
ATI Radeon x1950 Pro