server crash after karmic upgrade

[Tom H]

>> Yesterday I upgraded my home server to Karmic.
>> The upgrade seems to have completed correctly.  However, when I came
>> home today, the server was off line, could not be pinged , no samba,
>> no ssh, no intranet pages.  The only way to restart was from the power
>> switch.  After restart, everything worked fine.  There were some
>> upgrades I applied when I ssh'ed in to the box, all seemed well.
>> About an hour later, it was off line again.
>> At this point, I don't even know the right questions to ask or what
>> log files to check.  Any suggestions?  Tips for where to find more info?

> Not even a guess where to start looking?

The logs; start with kern.log or messages.log.