server crash after karmic upgrade

[Patton Echols]

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?