So, something like:
//-- Rebind my BBS to the BO MyBBS.BusinessObject = MyChildBO; }
You may also need to requery your grid to re-pull the data from the newly re-bound BBS after you do that.
Basically, what I think is happening is that the BBS (and therefore the grid) is getting bound to an empty instance of the childBO. The ChildFormDialog then creates a second instance of the childBO populated with the data from the parent form. Since the BBS is never updated to point to this new, populated instance, the data is not being reflected in your grid.