database files are incompatible with server, after computer restart

I installed and started PostgreSQL and it worked fine
for days. Then I restarted my computer and now I can't
start PostgreSQL ('pg_ctl -D pgdata -l pgdata/psql.log
start'). Here's what's in my log:

LOG: received immediate shutdown request
WARNING: terminating connection because of crash of
another server process
DETAIL: The postmaster has commanded this server
process to roll back the current transaction and exit,
because another server process exited abnormally and
possibly corrupted shared memory.
HINT: In a moment you should be able to reconnect to
the database and repeat your command.
FATAL: database files are incompatible with server
DETAIL: The database cluster was initialized without
HAVE_INT64_TIMESTAMP but the server was compiled with
HAVE_INT64_TIMESTAMP.
HINT: It looks like you need to recompile or initdb.

I guess my computer restart didn't agree with
PostgreSQL. But I've had crashes before and never had
a problem getting PostgreSQL going again. Anybody know
how to fix this? I also tried 'pg_resetxlog -f pgdata'
but still get the same error trying to start up.

Thanks,
csn
Mac OS 10.4.7
PostgreSQL 8.1.3

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