error vacuum full

I use postgres-8.3.5. My database has 168 GB in size. Whenever i try to do vacuum full happens the following error:
 
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.
vacuumdb: vacuuming of database "acotel_brazil_vas" failed: server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.

If i have autovacuum enabled, Do i need to do vacuum full?


Regards,
--
Ygor Degani