I was getting the Invalid Action error when trying to open Microsoft CRM 4.0.
And in the event log i could see the following entry.
Event Type: Error
Event Source: MSCRMKeyGenerator
Event Category: None
Event ID: 18949
Time: 4:59:35 PM
Current active key (KeyType : CrmWRPCTokenKey) is expired. This can indicate that a key is not being regenerated properly. Current Active Key : CrmKey(Id:6e254808-b21d-dd11-9041-001d7d22e1af, ScaleGroupId:00000000-0000-0000-0000-000000000000, KeyType:CrmWRPCTokenKey, Expired:True, ValidOn:05/09/2008 10:23:58, ExpiresOn:06/11/2008 10:23:58, CreatedOn:05/09/2008 10:23:58, CreatedBy:NT AUTHORITY\NETWORK SERVICE. Key Setting :
Starting the Microsoft CRM Asynchronous Processing Service on the server solved the problem for me!!!