Apparently, it is no longer safe (if it ever was) to use stderr to report "Windows procedure called during GC???????". This workaround prevents a crash, without hiding the underlying GC problem. src/ChangeLog addition: 2001-06-05 Paul Krause <pkrause(a)soundbite.com&gt; * event-msw.c: replace unsafe call to stderr_out with mswindows_output_console_string XEmacs Patch (cvs -q diff -u ): Index: src/event-msw.c =================================================================== RCS file: /usr/CVSroot/XEmacs/xemacs/src/event-msw.c,v retrieving revision 1.59 diff -u -u -r1.59 event-msw.c --- src/event-msw.c 2001/06/02 05:40:53 1.59 +++ src/event-msw.c 2001/06/05 11:13:15 ＠＠ -2065,7 +2065,7 ＠＠ behavior here. */ if (gc_in_progress) { - stderr_out ("Window procedure called during GC???????\n"); + mswindows_output_console_string ("Window procedure called during GC???????\n", 41); goto defproc; }