Postgres shutting down by itself...why?

I've recently installed Postgres 8.2.x on a RedHat Linux system. Everything
seems fine and normal. I can start and stop the server without errors.
When the server is running, everything appears normal. The problem is that
about every 2 to 3 hours I find the server is just not running anymore.
I've turned on logging at the info level and up and am not getting any
messages that is giving me any clue why the server is shutting down.

I get the following when I restart after I've discovered its down

LOG: database system was interrupted at 2007-11-29 14:25:48 CST
LOG: checkpoint record is at 0/43FBE0
LOG: redo record is at 0/43FBE0; undo record is at 0/0; shutdown TRUE
LOG: next transaction ID: 0/837; next OID: 32773
LOG: next MultiXactId: 1; next MultiXactOffset: 0
LOG: database system was not properly shut down; automatic recovery in
progress
LOG: record with zero length at 0/43FC28
LOG: redo is not required
LOG: database system is ready

The server is not even being used at this point. I can literally start the
server come back a few hours later and find its not running.

Any assistance, ideas, suggestions would be greatly appreciated. Thanks
all.