[ubuntu-in] system has become unstable

[Rohit V Bhute]

Hi all.

Since this morning, my system has either frozen up or restarted very 
frequently. The following events occurred - mostly in 2 bunches (1-2 and 
3-7).

1. Restarted when USB drive was inserted.
2. Freezed 2-3 minutes after login; using Thunderbird.
3. Mplayer exited suddenly.
4. Freezed before login prompt appears.
5. Restarted while playing file in mplayer.
6. In recovery mode, couldn't locate libc.so.6; apparently root partition
had disappeared.
7. GUI couldn't start because of some error (couldn't recollect exact 
error).
8. Lots of segfaults in /var/log/messages for today (5th Aug); but 
memtest gives zero errors over 1 pass.

RAM at least, is not to blame. Software is up-to-date.

In between the two bunches of events, for a stretch, system worked well 
for 3 - 3.5 hours. I have no idea where to start looking.

Any pointers will be appreciated.
-- 
Rohit V. Bhute
http://rvbhute.org