screensaver freezes system totally

[pete]

Hi all,

Having talked a friend into trying ubumtu 10.4 lucid (he's running the 
64 bit version), He is encountering a problem that I have never come 
across before.

Namely when the screen-saver has been running for about 20mins it 
freezes completely, and becomes totally unresponsive, only thing left is 
a hard reset!

His system spec are

AMD athlon dual core processor:
Nvidia graphics (dunno which 1) using Nvidia current driver
4gb ram

where would I find the relevant logs to try and start de-bugging this 
annoyance.

note I am running the same system (installed from the same live cd) with 
no issues and cannot reproduce his issue although my machine does differ 
from his in the hardware.

Any thoughts gratefully appreciated

Regards

Pete