First off, make sure you are not opening the file in the global scope of your script. If you are then do the following instead:
Code:
if viz.running():
#Perform file open operation
This will prevent Vizard opening the file twice. This should take care of your problem.
If you still need to detect Vizard exiting then handle the viz.EXIT_EVENT:
Code:
def onexit():
#Perform cleanup
viz.callback(viz.EXIT_EVENT,onexit)