Unable to start postmaster

I've installed v7.3.3 about 2 weeks back, everything was working fine.
Yesterday, when the server was rebooted (power failure), the postmaster
cannot be started up.

I tried the command as postgres user:
"pg_ctl start -D /usr/local/pgsql/data -l /usr/local/pgsql/data/serverlog"

which comes back with a reply "postmaster successfully started". However, a
check with "ps aux" shows it did not start at all.

The log file shows this error message:
FATAL:  'log_connection' is not a valid option name

I also try with the latest v7.3.4, same error.

Is there anything i can try to get postmaster to start?

Thanks,
David