Error message when you try to access Reports in Microsoft CRM 3.0: "Server Error in '/' Application"

When you try to access Reports in Microsoft Dynamics CRM 3.0, you receive the following error message:
Error An error has occurred. For more information, contact your system administrator.

If the DevErrors value is set to "On" in the Web.config file, you receive the following error message:
With Dev Errors: Server Error in '/' Application.

The request failed with HTTP status 401: Unauthorized.

To resolve this issue, check the following links:

1. Microsoft CRM 3.0: Additional Setup Tasks Required if Reporting Services Is Installed on Different Server.
2. How to configure IIS to support both the Kerberos protocol and the NTLM protocol for network authentication.