This has happened to me twice today. I have been editing a newly-created module in v3.1.13, saved it, closed Vassal and went away. When I wanted to resume work later, I got the “Eek!” screen (which BTW wouldn’t let me submit an error report) and the module will not open for either use or editing. Error log and module attached: they aren’t zips, the extension is just so it will attach.
Can it be rescued?
Incidentally I still have v3.0.17 on my PC (I am using Windows XP) and the module will open with that, although it warns me that “Unable to create class.VASSAL.build.widget.Pieceslot in [address of module] NoSuchElementException.”