diff -Nur -x '*.orig' -x '*~' metacity-2.22.0/src/core/display.c metacity-2.22.0.new/src/core/display.c
--- metacity-2.22.0/src/core/display.c	2009-04-22 08:28:20.000000000 -0400
+++ metacity-2.22.0.new/src/core/display.c	2009-04-22 08:29:21.000000000 -0400
@@ -4511,7 +4511,7 @@
     }
 
   tmp = workspace->mru_list;
-  while (tmp != start)
+  while (tmp != start && tmp != NULL)
     {
       MetaWindow *window = tmp->data;
 
