Colin Rafferty <craffert(a)ms.com> writes in xemacs-beta(a)xemacs.org:
 ...
 Anyway, this happens to me for my optimised and debugged version on
 IRIX, and my optimised version at home on Linux.  All of these were
 non-Mule. 
 The IRIX versions were compiled with SGI's compiler, and Linux
with
 gcc 2.7.2. 
Ditto for me, with Linux and Mule and pgcc 1.0.3 and 1.1.
If somebody can fix it in the very near future, the fix will go into
21.0, otherwise it won't.
The fate of whether I can get an XEmacs 21 out this month will be
determined tomorrow morning US/Pacific time, I'll pass on news as soon 
as I know.