This is usually caused by a forms cache corruption. Use the following steps
to resolve the problem.
1. In Outlook, go to Tools and choose Options.
2. Choose the Other tab.
3. Click Advanced Options
4. Click Custom Forms
5. Click Manage Forms
6. Click Clear Cache.
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Patricia Cardoza
Outlook MVP
Author - Special Edition Using Microsoft Office Outlook 2003
Lead Author - Access 2003 VBA Programmer's Reference
Author - Absolute Beginner's Guide to Microsoft OneNote 2003
http://blogs.officezealot.com/cardoza