I'm using VFP 7.0

I have a class with 2 sub-classes.

I'm trying to delete a shape control from the parent class that is not used in the sub-classes in any way.
After deleting the shape, I get "internal inconsistancy" error when I try to modify or use the sub-classes and VFP shuts down. I put the shape back into the parent class and everything is fine.

Can someone point me in the direction to find out what the problem is?

TIA