Microsoft outlook : The form requested to view this message cannot be displayed

Recently one of my users tried to enter an appointment into her calendar only to receive the following message : “The form required to view this message cannot be displayed. Contact your administrator”.

A reboot or updates won’t solve this error because the forms cache has become corrupted. The following fix worked a treat in Outlook 2003 so hopefully it will work for you too.
From the ‘Tools’ menu, select ‘Options’ and click on the ‘Other tab’.

Click on ‘Advanced Options’, which is in the ‘General’ section of the dialog

Now click on ‘Custom Forms’

Click on ‘Manage Forms’.

Click on Clear Cache