I have just converted an ASP.NET web application from .NET 3.5 (ASP.NET version 2.0.50727) to .NET4 and at ‘localhost’ development environment everything works fine but after installing the app from a setup (on a test machine running IIS6) one file remains hosted in IIS as in .NET2, thus crashing (with the error: ‘assembly built by a runtime newer than the currently loaded’) and the setting is fixed (I cannot change it from IIS).
All other files in the solution in IIS are automatically hosted in .NET4.
Any idea?