I do not see myself monkeying around with file associations for VASL. As I think is clear, this is driven by VASSAL and I am not inclined to move away from a consistent approach to VASSAL.
Sure, understood.
We have not yet isolated the cause of your recent crash. I hate to ask but if you could redo what you did and see if it crashes again, that might be helpful.
I can try to duplicate it but I think that will be very difficult due to the combination of events.
I think it was due to prior double clicking on a saved file for an OLD game that tried to access VASSAL 3.5.4 when it had been saved in VASSAL 3.2.17. That caused some major errors and subsequently corruption somewhere in VASSAL.exe (3.5.4) when I tried to save a file for NEW game I intended for testing. On top of that, there may have been an odd keystroke combo error as mentioned which triggered the crash of the save.
In fact, in those error messages from VASSAL, there was some notice that corruption was possible and that the VASSAL file might need to be recompiled. You should be able to duplicate that sequence of messages by saving a file in 3.2.17 then double-clicking on the file without using the open application to load it. If you have 3.5.4 installed also, then as I understand it (per Uckelman and yourself), the file will try to use 3.5.4 as the most recently installed version of VASSAL. You will see (and are already aware this will happen, I think) a messy cascade of error messages indicating a variety of failures -- sorry I don't have screen shots of that right now. One of the errors is persistent and cannot be shut down easily -- as per your warning of not double-clicking on files to open applications.
My assessment (involving the least amount of assumptions) is that what I reported as a crash was a subsequent error due to the prior double-click on the OLD save file (corrupting 3.5.4).
I say this because since then, I've reinstalled Vassal 3.5.4 and reconstituted the save file a second time (including Neal's table), which works fine now. Additionally, I've sent this save file to my computer-savvy opponent, who is also using VASSAL 3.5.4 and the 6.2.2-beta and he has had no problems with the file, either. However, we have yet to work with the file back and forth as we won't commence our game until next weekend.
Based on this experience, I think it may be problematic to test new versions of Vassal on a machine that has the old versions of Vassal, but I don't have a spare computer that is running windows 10; 99% of the use of Vassal is on this desktop, so it makes sense to use it.
[Edit -- as mentioned earlier, I could create a virtual machine with a memory partition of some kind, I have a vague idea of how to do it, but haven't tried it before and I might need some special software. Then I could use the virtual CPU structure to test the new Vassal module in isolation. Is this what you do?]