Its kind of a long story but my original PE1650 was running BIOS A10 when it died due to memory slot failure. So I borrowed a friend's unused PE1650 until I could get a "new" one on-site. Well, the new one was even older than mine and was running BIOS A05. I didn't think it was a big deal and installed Lenny (stable) and then upgraded to Squeeze (testing). And then the problems began. Let's just say that I spent a week of sleepless nights and frustrating days trying to figure out why the machine would just suddenly, and without any notice at all, freeze. And it wasn't your normal hang either as there was no kernel panic messages, no messages in the syslog, not even anything on the console.
I upgraded the BIOS to A11 (the latest available) and rebooted the machine; its been running now for almost 12 hours. This post may be a little premature as I've thought the problem was solved several times before, but everything was pointing to a hardware failure and the BIOS qualifies as hardware in my book. Regardless, I am still a little gun shy and will feel much better when it stays running for at least a whole day. A week would be better. :)