Cannot delete or backup message in Exchange mailbox

We recently setup a new Exchange 2003 box and brought over our
mailboxes from an SBS Exchange 5.5 box that's now gone.

The new Exchange 2003 box is being backed up using Veritas 9.1 onto
tape on a second machine. We use Symantec AntiVirus Corporate edition
(SAVCORP).

The backup job log shows a number of individual messages in certain
mailboxes that cannot be backed up. Many are in the deleted folder.

I've checked for each of these problem messages in their respective
mailboxes and folders using outlook and I cannot see any of them.

I've gone through and emptied the deleted folders on all of my users.
Veritas still sees them and tries to back them up and cannot.

Is it possible that these messages have been quarantined or marked by
SAVCORP and are in limbo? How can I kill them?

Thanks,
Eric