How to recover when can't start database

Hi!
(Hope this is the right place to post)

I crashed the postmaster and cannot start it anymore, with the error

 LOG:  database system was interrupted while in recovery at 2005-04-01 11:04:33 CEST
HINT:  This probably means that some data is corrupted and you will have to use the last backup for recovery.
LOG:  checkpoint record is at 5/6F00C540
LOG:  redo record is at 5/6F000ABC; undo record is at 0/0; shutdown FALSE
LOG:  next transaction ID: 599824; next OID: 147679259
LOG:  database system was not properly shut down; automatic recovery in
progress
LOG:  redo starts at 5/6F000ABC
PANIC:  btree_split_redo: lost left sibling
LOG:  startup process (PID 5603) was terminated by signal 6
LOG:  aborting startup due to startup process failure

Is there a way to recover from that?

I don't have a fresh backup, but loosing some couple of days won't be a
problem.

I use PG 8.0 on a linux box, with standard postgresq.conf (except some
increased memory settings).

thanks,
L.B.