ASP.Net method not found

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?

One thing you can check for is to make sure there are not two identical classes in your bin folder.

If you have this it can end up that one of them won't work, or both.

Also make sure that if its in code behind and not compiled that you reference the .vb file it resides in. If it is compiled into a .dll, make sure you do not have a .vb file reference.

(me being the guy doing the above-mentioned ASP.NET project).

there are no identical classes. only compiled dlls are referenced.

the ASP.NET page itself is very simple - it inherits some misc session stuff - and then attempts to call the certain method of the dll.

it happens on multiple machines (two different winxp-sp1 workstations, one win2003 server).

dlls are all residing the in bin/ dir and being registered into the GAC from there (not sure if necessary, but have been attempting to rule out possible causes).

can anyone offer *any* other suggestions as to what might be causing this?

also - have never be able to produce this error when debugging (and calling the method).