Unexpected Quits

[spector@mimsy.umd.edu (Lee Spector)]

I've been having MCL2.0b1p3 quit unexpectedly on me from time to time,
and I'm wondering if anyone knows what might be causing it.   All of the
MCL windows vanish and the finder gives me a message like "The application
 'unknown' has quit enexpectedly because an error of type 25 has occurred."
It's always type 25 and I think it always says the application is unknown.
I'm usually working in a saved application with a creator that I made up -
maybe that's why the application is unknown.  However, I think it has also
happened when I've launched MCL2.0b1p3 itself.  It only happens well into
a hacking session, and sometimes it happens right after GC, so I assume
it's some kind of memory error.  At first I blamed some (optimize (speed 3)
(safety 0)) declarations, but I've removed ALL optimize declarations and
it still happens.  My system is a Mac IIcx with 20 Megs running system 7.0 
with Mode32, 32-bit addressing, NO virtual memory, and a handful of other
extensions (mostly from the Now Utilities package). I generally run Lisp
in a 14 meg partition.  Any insights would be greatly appreciated!
  -Lee (spector@cs.umd.edu)