Oops, self.master.wait_window(self) doesn't help. I guess the newterd scripts will have to be able to handle an immediate return from their mainloop(). Sorry, I thought it was working because all the GUI stuff seemed to be working. Also, I noticed an oddity with Tkinter stuff that relies on 'variable changes', like Radiobutton's 'variable=foo, value=bar'. I had to change my stuff and add a 'command=' to those things.