Backup Exec Catalog Error

We use Veritas Backup Exec for our daily backups, which are completed correctly. However when we complete our morning checks we find the following error displayed in the applications log of Event Viewer.

Update to catalog index (d:\Program Files\VERITAS\Backup Exec\NT\Catalogs\BeTopCat.idx) failed.
Reason: Operation is not supported for this type of object. DAO.Workspace
d:\be\aruba\3311r\becat\server\catalogindex.cpp(289)

We have renamed the following files in directory winnt\programfiles\Veritas\Backup Exec\Nt\Catalogs
BeTopCat.idx (one file do not touch .db files)
********.Sm (approx three files)

This appears to solve the problem but after a while it starts all over again, please advise if you have any ideas.