Create IPSW stalls

I have SeasOnPass 0.8.3 (480) installed, and can’t seem to get by the “create IPSW” step. When I launch the app and invoke that function, a progress bar shows up for a brief second, and then nothing:

[[wysiwyg_imageupload:187:]]I’ve trashed the preferences and uninstalled the app to no avail. Thanks for any pointers!