Index: /trunk/src/VBox/Frontends/VirtualBox/src/runtime/fullscreen/UIMachineWindowFullscreen.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/runtime/fullscreen/UIMachineWindowFullscreen.cpp	(revision 27365)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/runtime/fullscreen/UIMachineWindowFullscreen.cpp	(revision 27366)
@@ -76,10 +76,15 @@
     updateAppearanceOf(UIVisualElement_AllStuff);
 
-    /* Make sure the window is placed on the right screen before we are going
-     * into fullscreen. */
+    /* Make sure the window is placed on valid screen
+     * before we are show fullscreen window: */
     sltPlaceOnScreen();
 
-    /* Show window: */
+    /* Show fullscreen window: */
     showFullScreen();
+
+    /* Make sure the window is placed on valid screen again
+     * after window is shown & window's decorations applied.
+     * That is required due to X11 Window Geometry Rules. */
+    sltPlaceOnScreen();
 
 #ifdef Q_WS_MAC
@@ -107,6 +112,6 @@
     move(r.topLeft());
     resize(r.size());
-}
-
+    qApp->processEvents();
+}
 
 void UIMachineWindowFullscreen::sltMachineStateChanged()