Maybe it was a bad idea to try to delete the ASG. Anyway, I did eventually get back into OOTP. I exported the imported schedule, and saw weirdness in the top-level SCHEDULE tag line.
That made me think there might be some sort of typo slipping by... Sure enough, I saw the very last two lines should be
Code:
</GAMES>
</SCHEDULE>
Those leading slashes are needed to make those closing tags that match the earlier opening tags. I was
sure that would fix things, but it was still doing the same thing after I changed the file. I might have a little more time here to experiment.