Slave server: FATAL: incorrect checksum in control file

Hi Guys,

   I'm trying to set up a warm standby server, but have problems with running it on the backup. I feel that I have done
likethe documentation says: 

   The WAL is being copied to the slave using rsync.
   Doing SELECT pg_start_backup(); (in psql)
   Copying the data directory to the slave (using rsync)
   Doing SELECT pg_stop_backup(); (in psql)
   Making sure the slave is using it's own postgresql.conf and the recovery.conf is set with the pg_standby command.
   .
   So far I don't get any errors, but when I start postgres on the slave (I'm using pg_ctl), I get the error 'FATAL:
incorrectchecksum in control file'. 

   Both servers are running PostgreSQL-8.3.5, configured with exactly the same options (just prefix and ssl).

   Any ideas ?

  Greetings,

 Leif