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