When moving a classlib between the versions, do an explicit "COMPILE CLASSLIB classlibname" before opening or using.

>I am writing a class in VFP 6. I week ago I copied the class to a VFP 5 project and I used - no problem. Today, I copied the last version of the class to the VFP 5 project and I got an error when I tried to open it: "mycontainer.vcx is not an object file".
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>There are 2 classes in the container. With VFP 6 I can open both classes. With VFP 5 I can open one of the classes but not the other (the one that I need, of course).
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>Any ideas?