annoying problem in 12.04

[compdoc]

>"restarting now.." and then the whole system was unresponsive.
>Anybody has ideas?


Computers have several common points of failure. The main ones are  the
power supply, the motherboard, RAM, cooling fans, and the hard drive.

Fans are easy - just make sure they are spinning at the proper speed. This
includes the fan inside the PSU.

If the motherboard is a few years old, it can develop bad capacitors. They
are easy to spot when you open the case. Any caps that are rounded on top or
leaking, are bad.  If so, replace the motherboard. Here are some sample
pictures:

http://en.wikipedia.org/wiki/Capacitor_plague

Cheap power supplies often develop bad caps inside too but it might be
dangerous to open the PSU, so just swap it out to test. RAM you can test for
free by booting memtest86 and letting the tests run overnight. 

The hard drive is easy: there's no need to run any tests - you just read the
drive's SMART info. It records when sectors are failing, and when other bad
things happen. 

If you need help with the SMART data, you can post the results here and we
can tell you what's going on.