Your backup is from a different version of Windows SharePoint Services and cannot be restored to a server running the current version. The backup file should be restored to a server with version '12.0.0.6335' or later.

It sounds like an odd error but lets face it. STSADM backups are not service-pack independent. It just reminds me of restoring SQL Server system databases. Remember that you need to have identical service packs on source and destination of the backup. Otherwise your restore shows you this.

Check this little post by Aaron Saikovski to get your exact solution.

Cheers
Alireza