Patch from Travis Watkins
https://bugzilla.gnome.org/show_bug.cgi?id=530702

diff -ru metacity-2.27.0/src/core/screen.c metacity-2.27.0.new/src/core/screen.c
--- metacity-2.27.0/src/core/screen.c	2008-10-19 16:15:38.000000000 -0500
+++ metacity-2.27.0.new/src/core/screen.c	2009-08-24 04:56:26.929023537 -0500
@@ -2782,11 +2782,14 @@
   char selection[32];
   Atom a;
 
+  screen->wm_cm_timestamp = meta_display_get_current_time_roundtrip (
+                                                               screen->display);
+
   g_snprintf (selection, sizeof(selection), "_NET_WM_CM_S%d", screen->number);
   meta_verbose ("Setting selection: %s\n", selection);
   a = XInternAtom (screen->display->xdisplay, selection, FALSE);
   XSetSelectionOwner (screen->display->xdisplay, a, 
-                      screen->wm_cm_selection_window, CurrentTime);
+                      screen->wm_cm_selection_window, screen->wm_cm_timestamp);
 }
 
 void
@@ -2797,6 +2800,7 @@
 
   g_snprintf (selection, sizeof(selection), "_NET_WM_CM_S%d", screen->number);
   a = XInternAtom (screen->display->xdisplay, selection, FALSE);
-  XSetSelectionOwner (screen->display->xdisplay, a, None, CurrentTime);
+  XSetSelectionOwner (screen->display->xdisplay, a,
+                      None, screen->wm_cm_timestamp);
 }
 #endif /* HAVE_COMPOSITE_EXTENSIONS */
diff -ru metacity-2.27.0/src/core/screen-private.h metacity-2.27.0.new/src/core/screen-private.h
--- metacity-2.27.0/src/core/screen-private.h	2008-10-19 16:15:38.000000000 -0500
+++ metacity-2.27.0.new/src/core/screen-private.h	2009-08-24 04:50:41.469785283 -0500
@@ -113,6 +113,7 @@
 
 #ifdef HAVE_COMPOSITE_EXTENSIONS
   Window wm_cm_selection_window;
+  guint32 wm_cm_timestamp;
 #endif
 
   guint work_area_idle;