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

I'm working on NopCommerce 2.30.
I've just set Command Timeout to 600 in NopObjectContext.cs.I've build only Nop.Data project and deploy it to production site.I got an error  
`Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.` when trying to access home page.

It is working fine,when I rollback old Nop.Data dlls.

What could be the reason?