I have a set of dlls used in both windows forms and ASP.Net. Some of these DLLs are required to reside in the GAC. (They handle business logic)

The crux of the problem is that the asp.net pages will seemingly randomly pop up with method not found when a workmate modifies the code behind for a website. The method it is complaining about is integral to the system and has been in there for a very long time.

Normally I would say that this is a version issue however I cannot replicate the error on my own machine and the windows forms have never had this issue. Sometimes resetting IIS resolves the error. I make sure the guy removes dlls from the GAC and re-adds them every time he gets a new update.

Any ideas?