Notes/Domino 6 and 7 Forum : R6.0.3 mail.box corruption

I've done some searching and can't find posts dealing with my issue, so here goes. If this has been dealt with in another post, please point me in the right direction.

Server:

Dell 2650 dual xeon
2GB ram
Plenty of hd space.
Domino 6.0.3 Enterprise

The issue I am having is that in the last 2 weeks, our mail.box (we only use one) has become corrupt 5 times. The logs don't show anything specific other than "MIME to CD error (Process: Router (########.########), Database: d:\notes\data\mail.box, Note: ########): Database is corrupt -- Cannot allocate space". The corruption seems to happen around the same time, but doesn't happen every day. Below is what runs on my server at night:

1. 9:00pm Veritas BackupExec 9.0 w/Domino agent.
2. 1:00AM fixup
3. 3:00AM compact
4. 6:00AM updall

The corruption seems to happen around the same time the server is being backed up. Has anyone had an issue with Veritas/corrupt databases? I have read that the compact job can also cause corruption in mail.box if there is an invalid attachment on an email. Would it help to run 2 mail boxes? Our only solution so far has been to run a fixup, if that fails, down the server, rename the file, and let it create another one. This is getting frustrating being we are the hub for 8 other servers.

Any help or a point in the right direction would be appreciated. Thanks.