Thanks to all suggestions. Dragan gave me a hint that helped me - I realised that the classloc needed to be "..\myclass.vcx" rather than just "myclass.vcx". Not being in the correct path made VFP leave it open.

Cheers,
Jamie

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>You may try to compile each classlib explicitly, before doing any editing or building. VFP may be detecting a conflict between the content of class/classloc and the compiled properties, and thus giving this message.