You install the Microsoft Conferencing Add-in for Microsoft Office Outlook. After you do this, the Microsoft Outlook forms cache file (Frmcache.dat) is deleted every time that you close Outlook.
To resolve this issue, install update 948738.
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
948738 Description of the update for the Conferencing Add-in for Outlook: April 11, 2008