[Ti] system instability

[silvo conticello]

I've recently noted an increase in system instability:
sometimes applications start crashing one after the other until I get 
pissed off and restart the computer.
Once I ask the restart usually it just log-out and re log-in.
After a further restart command it finally restart.

This has happened already 3-4 times in the past months. I haven't added 
RAM at this time (I've added 1Gb 6 months ago, few weeks ago I've 
re-tested it with the Apple Hardware Test CD).
It might be that the instability follows hard use of the computer 
and/or a period with only 5Gb free on the HD (I don't remember if this 
has been a constant).

Any guess on what's going on?

Thanks,
Silvo

Silvo Conticello
Albook 17" 1.5GHz/1.5Gb RAM/80Gb HD/OS10.3.8
iMac 1GHz/500Mb Ram/80Gb HD/OS10.3.8/17" display
Cambridge UK