Index: src/window.c
===================================================================
RCS file: /usr/CVSroot/XEmacs/xemacs/src/window.c,v
retrieving revision 1.41.2.48
diff -u -r1.41.2.48 window.c
--- src/window.c 2000/05/03 14:47:19 1.41.2.48
+++ src/window.c 2000/05/05 19:40:21
@@ -1875,7 +1875,13 @@
 window_unmap_subwindows_cache_mapper (Lisp_Object key, Lisp_Object value,
 				      void *flag_closure)
 {
+  struct frame* f = XFRAME (XIMAGE_INSTANCE_FRAME (value));
   unmap_subwindow (value);
+  /* In case GC doesn't catch up fast enough, remove from the frame
+     cache also. Otherwise code that checks the sanity of the instance
+     will fail. */
+  XWEAK_LIST_LIST (FRAME_SUBWINDOW_CACHE (f))
+    = delq_no_quit (value, XWEAK_LIST_LIST (FRAME_SUBWINDOW_CACHE (f)));
   return 0;
 }