so let me get this straigt... you subclass Kbizobj to MKbizobj, then subclass MkBizObj to various other bizobj's. You can add a method to Kbizobj, but not to MkBizObj, and you may also add a method to subclasses of MkbizObj?

Have you tried opening the vcx out side of the MM framework and editing it? Then putting it back in? From what you are saying, you put the method in and it's actually in there, but when you run it, it's not there and the error given is for a property. I've seen this before, but without the error message. It's like there is some sort of lock on compiling the vcx.
Have you tried rebuilding the vcx that the MKBizObj belongs in???
I'll do the same thing that you are doing to see what happends..