> Since I did not see this a few weeks ago, perhaps it's time to bite the
> bullet and bisect.

I'll start bisecting, but since the crash is so infrequent and
unpredictable, I'm not sure what criteria I should use for marking a
commit "good".  Use Emacs normally for 72 hours, and if it doesn't
crash, then it's probably okay?  That might take me a while.