I wouldn't be to worried about getting into the php end working, I would be worrying about why there are so many null reference errors, I would be checking just how the php calls are being made, are loop conditions working correctly. Overall I think that the multitude of errors that are apparent the moment the swf starts would probably big a big part of whatever slowdown issues you are having..
I checked out the app , it didnt hang for me , but I only got the address screen. Like David said , that null pointer exception is unsettling. Did this individual also write the backend (PHP) too ?
The "Hang" happens after people fill out the form and hit submit in the very last step.
I do appreciate the "debug" info. We are troubelshooting those errors already.
Thanks again. Keep ideas coming if anyone has any other suggestions.