Testing running several slightly different sets of programs proved to
my satisfaction that the culprit is X.  Specifically, when running the
X server, if I shutdown now or kill -s TERM 1 I can wait five minutes
and still my system will be unresponsive to the keyboard and
apparently hung.  X will shut down, but that's it.  I'm using X11R6 as
shipped with NetBSD 1.3.2 for i386, on a machine with a K6 300MHz chip
and 64MBs of RAM.

If I don't run X I can get into single-user mode with no difficulty.

Any thoughts on how I can remedy this, or what further information I
should provide?  Should I take this question elsewhere?

All the best,
James Wetterau