Index: /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIFrameBuffer.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIFrameBuffer.cpp	(revision 55138)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIFrameBuffer.cpp	(revision 55139)
@@ -520,5 +520,5 @@
     , m_pMachineView(NULL)
     , m_iWinId(0)
-    , m_fUpdatesAllowed(true)
+    , m_fUpdatesAllowed(false)
     , m_fUnused(false)
     , m_fAutoEnabled(false)
@@ -831,7 +831,8 @@
         return E_FAIL;
     }
-
-    /* Directly update m_image: */
-    if (m_fUpdatesAllowed)
+    /* Directly update m_image if update fits: */
+    if (   m_fUpdatesAllowed
+        && uX + uWidth <= (ULONG)m_image.width()
+        && uY + uHeight <= (ULONG)m_image.height())
     {
         /* Copy to m_image: */