SuSE 10.1 hang

Hello, I'm running SuSE 10.1 with the latest updates on Opteron 148, ASUS SK8N with nForce3 and 2x 512MB Super Talent DDR333 Registered ECC. I'm experiencing hangups - everything freezes and nothing can be done. I think it may be a hardware problem, because yesterday there were several thunderstorms, but I'm not aware where to look and what to look for in order to identify it. What have I done: - memtest says nothing for half an hour; may be I should let it work more time; - mcelog says nothing; - /var/log/messages has nothing suspicious; Any help will be appreciated. Many thanks, Mitko