Index: include/ntuser.h
===================================================================
--- win32ss/include/ntuser.h	(revision 66208)
+++ win32ss/include/ntuser.h	(working copy)
@@ -638,6 +638,7 @@
 #define WNDS2_FORCENCPAINT              0X00400000
 #define WNDS2_FORCEFULLNCPAINTCLIPRGN   0X00800000
 #define WNDS2_FULLSCREENMODE            0X01000000
+#define WNDS2_DESTROYMSGSENT            0X02000000
 #define WNDS2_CAPTIONTEXTTRUNCATED      0X08000000
 #define WNDS2_NOMINMAXANIMATERECTS      0X10000000
 #define WNDS2_SMALLICONFROMWMQUERYDRAG  0X20000000
Index: user/ntuser/window.c
===================================================================
--- win32ss/user/ntuser/window.c	(revision 66208)
+++ win32ss/user/ntuser/window.c	(working copy)
@@ -486,7 +486,7 @@
 
    if(Window->state2 & WNDS2_INDESTROY)
    {
-      TRACE("Tried to call IntDestroyWindow() twice\n");
+      TRACE("Tried to call co_UserFreeWindow() twice\n");
       return 0;
    }
    Window->state2 |= WNDS2_INDESTROY;
@@ -511,25 +511,37 @@
    }
 
    /* free child windows */
-   Children = IntWinListChildren(Window);
-   if (Children)
+   for (;;)
    {
-      for (ChildHandle = Children; *ChildHandle; ++ChildHandle)
+      BOOL GotOne = FALSE;
+      Children = IntWinListChildren(Window);
+      if (Children)
       {
-         if ((Child = IntGetWindowObject(*ChildHandle)))
+         for (ChildHandle = Children; *ChildHandle; ++ChildHandle)
          {
-            if(!IntWndBelongsToThread(Child, ThreadData))
+            Child = IntGetWindowObject(*ChildHandle);
+            if (Child == NULL)
+               continue;
+
+            if (!IntWndBelongsToThread(Child, ThreadData))
             {
                /* send WM_DESTROY messages to windows not belonging to the same thread */
+               if (Child->state2 & WNDS2_DESTROYMSGSENT)
+                  continue;
                IntSendDestroyMsg(Child->head.h);
+               Child->state2 |= WNDS2_DESTROYMSGSENT;
             }
             else
                co_UserFreeWindow(Child, ProcessData, ThreadData, SendMessages);
 
             UserDereferenceObject(Child);
+            GotOne = TRUE;
+            break;
          }
+         ExFreePoolWithTag(Children, USERTAG_WINDOWLIST);
       }
-      ExFreePoolWithTag(Children, USERTAG_WINDOWLIST);
+      if (!GotOne)
+         break;
    }
 
    if(SendMessages)