Did you add dll via nuget feed? Can you verify that dll has "8fe83dea738b45b7" as public key token? What about other Find assemblies? The same key?
This seems to be a bit strange. Do you get this error after installing with the Nuget package or how did you do the install?
This was the result after updating according to http://tedgustaf.com/blog/2013/12/how-to-upgrade-to-episerver-75/, after getting all nuget packages. Did rollback and retried several times now without result (making sure web.config was up to date).
I have a very irritating issue, which I cannot seem to resolve.
I have added the proper .dlls as references and they are located in bin-folder, but they still cannot be loaded correctly.