If your website is hosted on IIS6/HELM you will need to contact support to add a script mapping for MVC to your specific website.
All IIS7 servers support MVC out of the box as the MVC script mapping is in the web.config, but to use this you must be using the integrated pipeline mode.
In DotnetPanel goto websites and select the website in question. Next, click on the extensions tab and change the dropdown box for ASP.NET to 2.0 Integrated Pipeline. This will allow IIS7 to use the script mappings defined in your web.config.
If you see the following Security Exception
Description: The application attempted to perform an operation not allowed by the security policy. To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file.
Exception Details: System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.ReflectionPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.
Then you will need to update the trust level for your website. You can do so by reviewing this KB article: http://support.webecs.com/KB/a672/changing-the-default-aspnet-trust-level.aspx
Article ID: 778, Created On: 4/11/2010, Modified: 4/11/2010