First thing I would try is to clean up the forms cache.

To do so, follow these steps:
     1. On the Tools menu, click Options.
     2. Click the Other tab, and then click Advanced Options.
     3. Click Custom Forms.
     4. Click Manage Forms.
     5. Click Clear Cache.
     6. Close all open windows, and then restart Outlook 2003.

If the above does not work, try the following.

Deleting the Forms Cache File:
The Frmcache.dat file is the primary file to delete. The Frmcache.dat
file serves as an index of the individual forms that have been cached
on the computer. Use the following steps to manually delete the
Frmcache.dat file. In addition, these steps delete all of the cached
forms on your computer, which are stored in subfolders of the
Forms folder.

 1.. Quit Outlook.
 2.. Search the Hard drive (<F3>) to locate the Frmcache.dat file.
      (Be sure to check in HIDDEN files on W2K or WXP.)
 3.. Delete all that are found from the FIND window.
 4.. Open Outlook.

When you restart Outlook, and use a form, the forms cache
is re-created. Sometimes your forms cache (where outlook gets its info
on how to build the form) gets corrupt. The deletion of the forms cache
is simply a forced "rebuild" of your forms to remove any "corrupted"
forms that you may have in your cache information.

Nikki Peterson