"For a couple of weeks, I have had constant crashes of all my 
applications on Lucid:

     * Thunderbird 3.1 (updated since crashing started using Ubuntuzilla)
     * Firefox 3.6.6 (updated since crashing started using Ubuntuzilla) 
- also crashes in safe mode
     * OpenOffice 3.2
     * Opera 9.63

Most frequently it is Firefox and Thunderbird crashing, because they're 
the applications I use most. (Also F-Spot has crashed, but F-Spot 
frequently crashed before all this, so may not be related).

Sometimes applications will run for a few hours and then crash (either 
suddenly close or freeze, it varies). Other times the application 
crashes before it even opens, and I just get the Mozilla crash reporter. 
If an application won't start at all, it will usually start if I restart 
the computer, but may crash again soon afterwards. There is no obvious 
pattern to when it crashes - sometimes on starting, sometimes when I 
click something, sometimes when I'm not even at the computer and I just 
come back to find it crashed."

#1 at
http://ubuntuforums.org/showthread.php?t=1530611&highlight=crash





I'm thinking it's a hardware problem...