I think I have found my problem and I'm pretty sure it has to do with a flaw in the way we use SET CLASSLIB rather than the way I was creating my new class. Could those of you who know far more about the inner workings of VFP than I please confirm the following for me?

When an EXE does a SET CLASSLIB a list of the available classes is built in memory. Assume you build an APP file and compile the VCX files into it. If the APP file called by the EXE tries to instantiate a class the in-memory list of available classes is searched. If the class definition is not in the version of the class library when SET CLASSLIB is issued, you get a "Class Definition Not Found" error. If it was there, the definition compiled into the APP file is used to create the class.

(In our case, my "Class Definition Not Found" error disappeared when I issued a new SET CLASSLIB when this particular app starts.)

Thanks..........Rich