I have a very similar system, (Athlon 1800+, Matrox G550 dualhead) and apparently the same problem. I have heard that Athlons like this suffer from overheating, so I assumed it was that.
It freezes sometimes when there is a lot of system activity, so I put in more fans. While it hasn't helped much, I haven't ruled out overheating.
But I've never tried ACPI modules. It sounds good to me ....
I've tried removing the G400 too just incase it was the video card overheating (I replaced it with a PCI S3) but it froze too (rather quickly I might add). I also ran lm-sensors overnight and left it as "sticky" on my desktop and on the upper layer, so that if it freezes I'll see what temperature it last recorded. It was 0C degrees when it crashed last night.
I've had acpid running with the relevant ACPI modules installed for processor, system, etc since last night but it still froze overnight.
As I said in a previous email, I'm downloading Knoppix now to try and rule out whether it could be the OS doing it. As you can see, I'm going to all lengths to stop this annoyance :)
Best regards, Gonzalo
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