Only Tech Note I can find ( http://seer.support.veritas.com/docs/260761.htm ) just says to inventory before running the catalog job, but you siad you've done that.
This is kind of a stretch, but shut down the BEWS services, rename the catalogs folder (catalogs.save) and restart the services
BackupExec should create a new \Catalogs folder, and you should be able to inventory and catalog the old tape(s)
After the catalog succeeds (if it does) shut down the services and copy the U01 file(s) to the original catalog folder, rename back to \Catalogs, delete the BETOPCAT.IDX file and restart the services
(Or if this is a one time thing, just do your restore)