CHDKPTP does some of its work by running scripts on the camera itself. So you can't be running your own script when you try to connect. However,AFAIK you can launch your script once you are connected.
To elaborate slightly, for anyone else who runs into this issue:
The chdkptp GUI runs script on connect to update the mode dropdown. If this fails, it will connect but the GUI state will be confused, and live won't work.
The CLI doesn't run any script on connect.
Running a script after connecting should be fine, although most of the buttons and commands wont work, because they use camera side script.
edit:
In chdkptp r693 and later, only the mode list should be affected if you start the GUI with a script running.
