Hi Viv,don't forget all this was very new to me ( not now !!! ) and I didn't understand what the Web.config file in the Views folder was for and why there was another one in the root, my solution has three projects and each has its own Web.config and I think one was referencing a different version of the assembly than the other one, and yes I did change to 4.5 one of the projects was using 3.5 so I made them all use 4.5 - why does all this remind me of dll hell ? Stay tuned and keep the help line open looking at WAS next.