I am dying to find the keystroke that causes this, so if anybody can
give me tips on what to do...
There is some sequence of keystrokes, involving at least C-x C-n and
probably C-g and C-c. When I type them (whatever they are), Emacs is
completely frozen and must be killed from the Terminal. I know that
C-x and C-n are involved, because I usually see a message about "Goal
column not being activated" in the frozen Emacs. However, just
playing around with these control keys myself does not cause the
problem. Also, I only trigger this sequence 1-2 times a day, so it
is rare. My own attempts have not caused the hang.
Debugging pointers?