Cause
This error occurs if there is an attempt to delete an exclusive collection. Exclusive collections cannot be explicitly deleted.
When you add a reference to a class and that reference is a collection, it is normally treated as an exclusive collection. The exception to this is when the reference has no inverse and you explicitly uncheck the Exclusive check box in the Define Reference dialog.
An exclusive collection is inherently bound to its parent object; that is, it is created when the parent object is created and deleted when the parent object is deleted. It cannot be assigned to, it cannot be referenced from any other object, and it cannot be explicitly deleted.
Action
Change your application code to remove the invalid deletion.
If the collection has no inverse and you did not intend it to be exclusive, modify it by unchecking the Exclusive check box in the Define Reference dialog. The collection is then shared; that is, you have to create the collection before you use it and then delete it when it is no longer required.