mysterious system lockups in gutsy

[John Baker]

Hello

I work on a computer that I built from parts over the summer. For its 
first four mounts of life it used Kubuntu Edgy without a hitch. But as 
soon as a installed Gutsy it started randomly locking up. The whole 
system becomes entirely unresponsive and cannot even be pinged over the 
network.

It is the sort of error that I would assume was due to bad memory or 
something similar but I can reboot to the Edgy partition and run it 
again without a hitch.

Also, this happens whether running KDE without compiz or running Gnome 
with it. (Though both have the proprietary nvidia driver installed so 
that could be an issue)

Nothing at all shows up in the system logs at the time of the lockup.

I'm at a loss as to how to begin diagnosing the problem. Can anyone 
offer some suggestions?

Thanks

John