Index: /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIMouseHandler.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIMouseHandler.cpp	(revision 50785)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIMouseHandler.cpp	(revision 50786)
@@ -556,5 +556,5 @@
                     {
                         QPoint posInViewport = pViewport->mapFromGlobal(pOldMouseEvent->globalPos());
-                        if (pViewport->geometry().contains(posInViewport))
+                        if (pViewport->geometry().adjusted(0, 0, 1, 1).contains(posInViewport))
                             probablyHoveredViewports << pViewport;
                     }