Postgresql 7.1 Beta 5, Postmaster dead

Woke up this morning and my DB was no longer accepting connections.
The postmaster had stopped running.  Here are my log files, the old
one first.

--- old log ---
Lock file "/usr/local/pgsql/data/postmaster.pid" already exists.
Is another postmaster (pid 450) running in "/usr/local/pgsql/data"?

--- fresh log ---
DEBUG:  starting up
DEBUG:  database system was interrupted at 2001-03-08 09:57:30
DEBUG:  CheckPoint record at (0, 29799500)
DEBUG:  Redo record at (0, 29799500); Undo record at (0, 0); Shutdown
FALSE
DEBUG:  NextTransactionId: 56058; NextOid: 38568
DEBUG:  database system was not properly shut down; automatic recovery
in progress...
DEBUG:  ReadRecord: record with zero len at (0, 29799564)
DEBUG:  Formatting logfile 0 seg 1 block 1589 at offset 5260
DEBUG:  The last logId/logSeg is (0, 1)
DEBUG:  redo is not required
DEBUG:  database system is in production state

-- end --
Any thoughts what may have casued this?  This database has been
running uninterupted for days, although it may have had a bit more
traffic today.

Thanks!

Ryan Mahoney