After installing a CRM 4.0 ISV Add-on to my Dynamics CRM 2011 Beta 1 server (foolish I hear you say!), I was presented with the following:
Server Error in Application "MICROSOFT DYNAMICS CRM"Internet Information Services 7.5
HTTP Error 404.0 - Not Found
The resource you are looking for has been removed, had its name changed, or is temporarily unavailable.
It seems that the IIS7 CRM Application pool had been modified to revert back to using the version 2 framework. To resolve:
1. Open IIS 7 Manager
2. Navigate to the CRMAppPool and double click on it to enter the Basic Settings.
3. Change the Framework version to be v4: