Diagnostic tools for tracking down machine freeze

[Nigel Henry]

I've always had the odd freeze up on this new machine of mine, but mainly with 
some distros, like Archlinux for example. But now I'm getting frequent 
freezeups on Kubuntu Dapper, and Debian Etch was freezing up after about 5 
mins.

I've been running Dappers Memtest86+ v1.70 for over 10hrs now. 14 passes done 
with no errors, so the memory appears to be ok, and the machine hasn't locked 
up.

This machine is on a KVM switch with another machine which is infrequently 
booted up. Are KVM switches known for creating such freezeups?

Any suggestions as to diagnostic tools I could use to try and track down the 
problem?

When Archlinux freezes up, and I do a hard reset, I have to run fsck because 
disk errors are seen, and one thing stands out. It says last write to disk 
was 2 hrs in the future. Would that be due to the hard reset? We were in CEST 
at the time which would be UTC +2, so the system time would be effectively 
2hrs in the future compared to the hardware clock.

Machine details below:
Asus M2N-X Plus mobo.  (Nvidia Geforce 61)
AMD Athlon 64 processor (single core) (all OS's are 32bit)
2x1GB Crucial Ballistix DDR2 memory (Memtest86+ says, 401MHz (DDR803)
Asus EAX1550 Silent graphics card, with 512MB DDR2. PCI-e
160GB sata harddrive
250GB sata harddrive
Q-TEC 550W Dual Fan PSU. This is 20 pin plus 4 pin, and the mobo is 24 pin 
plus 4 pin. The mobo manual does mention that if you use a PSU with 20 pins, 
ensure that the 20 pin connector can supply at least 15A for +12v, and has a 
minimum power rating of 300W. Not sure how I could verify if the 20 pin 
connector is capable of providing 15A on the +12v rail.

The manual does say that the system may become unstable, or fail to boot if 
the power is inadequate.

Any suggestions welcome.

Nigel.