Have developed an asp.net 3.5 application which consists of a we-site, some developed assemblies and some 3rd party assembles such as Telerik, Jayrock etc, all very much standard 3rd party apps. Created and built this app, tested on Win 2008 Eval running on a VM, all fine. Imagine my frustration when after installing on clients production Win 2008 server, that the app could not run and the error message was the "Strong name signature could not be verified. The assembly may have been tampered with, or it was delay signed ..." one. This was for all assembles in app (removed one and this kept popping up for a different assembly). Attempted to install on a machine on the network and received the same error. I am fairly baffled and a little freaked as I can not figure this out and time is rapidly running out. Have inspected all parts of server I know about (.NET, IIS7) but all seems fine. What could cause this? It sounds like there is a stricter security manifest on the production server - but where would I look and for what? It must be a group policy. only other item is that the machines are running Symantec ante-virus. The IT head is on hols so can't quiz him which is also frustrating - but as they say time waits for no man!