Error message when you use the Microsoft Dynamics CRM 4.0 SDK to develop a Custom Workflow Activity assembly: "The Key cannot be NULL"

When you use the Microsoft Dynamics CRM 4.0 Software Development Kit (SDK) to develop a Custom Workflow Activity (CWA) assembly, you receive the following error message: This problem occurs if the following conditions are true:

• You use some output parameters in a condition of a workflow.
• The output parameters that you use include one of the following types:
  • Picklist
  • Boolean
  • Status

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 has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base: For more information about Microsoft Business Solutions CRM software hotfix and update package terminology, click the following article number to view the article in the Microsoft Knowledge Base: