When you upgrade from Microsoft Dynamics CRM 3.0 to Microsoft Dynamics CRM 4.0, you receive the following error message:
Action Microsoft.Crm.setup.Server.DeleteHotFixesAction failed.
Object reference not set to an instance of an object.
This problem is fixed in the latest cumulative update rollup for Microsoft Dynamics CRM 4.0. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
Microsoft Dynamics CRM 4.0 updates and hotfixes