Looks like it is specific to dosbox somehow. With the earlier versions of the index program, even fullscreening an independent dosbox launch while the program is running causes the crash. That is true even if I launch notepad first. But if the program launches notepad from inside then there is no issue (except that notepad is open). With the latest program, I'm launching another mmf program and killing it before dosbox launches, and that works. But I think it was working in one of my versions so long as I do it before dosbox fullscreens. A little more elegant to do it before I launch a dos game at all though.
With regard to notepad, I meant to say that an independent launch of notepad accomplishes nothing, but launching notepad within Fusion (by launching a designated text file) works, except of course, the text file is open.
Somehow the index program is getting tangled with dosbox from the get go. As long as dosbox is windowed, no problem, but fullscreen causes issues. But if I launch and kill another mmf program, then the problem is solved.
I'm wondering if this has anything to do with the resolution of the index program. It's 1900 x 900. In at least some of the earlier versions, the dosbox crash causes the index program to resize to what may be 640 x 480.