After recieving the error message "Could not load file or assembly 'App_Web_, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified." I found an article [link below] which simply states to clear down your temporary .net files. This worked a treat. I beleive the problem was from previous compilations that had not cleared down properly and the files had become locked. If you are unable to remove the files run an "iisreset" and try again.