Outlook – Calendar – The form required to view this message cannot be displayed.April 23, 2007
Option 1 Solution
Delete the Frmcache.dat from the location as stated below :
C:\Documents and Settings\user_profile\Local Settings\Application Data\Microsoft\FORMS
To Delete the Frmcache.dat File
Click Start , point to Find , and click Files or Folders .
Type “Frmcache.dat “in the Named box, and click Find Now .
Click to select the file and press DELETE to remove each instance of the file.
Option 2 Solution
Use the ForceFormReload registry key
When the forms cache seems to cause problems sporadically, and you cannot determine the cause of the problem, you can to set the ForceFormReload registry key in Outlook. When the ForceFormReload registry key is enabled, and Outlook encounters an error when opening an item that is based on a custom form, Outlook automatically clears the cache for this specific form.
Then, Outlook tries to open the item again. While this method does not correct the cause of the forms cache problem, this method does make the problem transparent to people who use custom forms.
To enable the ForceFormReload registry key functionality, follow these steps:
Start Registry Editor.
Click the following key in the registry:
On the Edit menu, click Add Value, and then add the following registry value
Value : ForceFormReload
Data Value : Reg_Dword
Value Data : 1
Signing Off Now