Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.

This is a classic unhelpful error and nightmare. Anyway, when publishing a mvc 3 application you do not have all the requored mvc3 files on the server that is hosting your site.

The best advice I got and what actually solved the problem can be found here.

http://www.britishdeveloper.co.uk/2011/05/mvc3-deploy-could-not-load-file-or.html

Hope it helps!

 

UPDATE:

Ok, so none of the “copy local” worked for me. What did was using the deployment package that is build through my Visual Studio Solution and deploying to IIS. finally worked.