I think your problem is the reload, when this happens the window probably loses all relationship references (I'm guessing). If the parent refreshes, it makes sense that your code no longer controls the child. With this in mind it seems logical that the opposite is also true.

I imagine you have two options:
1. Use a frame in the child window so the child doesn't reload, only its contents (this may or may not be helpful?).
2. Use a variable or function in the child window to register the parent (this assumes that a link still exists from parent to child, even though the link is broken from child to parent).

Cheers.