Ok it seems you'll have to recreate your mailbox store:
1. Back up the Exchange 2003 Mailbox database first in case something goes wrong. If you are using NTBackup utility, try the online backup method in the following KB article:
XADM: How to Back Up and Restore an Exchange Server Computer by Using the Windows Backup Program
http://support.microsoft.com/?id=2582432. Use Exmerge to export all the mailboxes to PST files. Refer to the following Knowledge Base Article for more information about Exmerge:
XADM: Microsoft Exchange Mailbox Merge Program (Exmerge.exe) information
http://support.microsoft.com/kb/174197How To Recover or Restore a Single Mailbox in Exchange 2000 Server
http://support.microsoft.com/?id=8133373. Rename the mailbox database file and mount a new store.
4. Restore the mailbox from PST files and test the issue again.