Index: /trunk/src/VBox/Frontends/VirtualBox/src/globals/VBoxGlobal.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/globals/VBoxGlobal.cpp	(revision 48276)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/globals/VBoxGlobal.cpp	(revision 48277)
@@ -964,12 +964,13 @@
 {
     /* Search for corresponding UI medium: */
-    UIMedium uimedium = cmedium.isNull() ? UIMedium() : medium(cmedium.GetId());
+    const QString strMediumID = cmedium.isNull() ? UIMedium::nullID() : cmedium.GetId();
+    UIMedium uimedium = medium(strMediumID);
     if (!cmedium.isNull() && uimedium.isNull())
     {
-        /* UI medium may be new and not in medium-list, request enumeration: */
+        /* UI medium may be new and not among our mediums, request enumeration: */
         startMediumEnumeration();
 
         /* Search for corresponding UI medium again: */
-        uimedium = medium(cmedium.GetId());
+        uimedium = medium(strMediumID);
         if (uimedium.isNull())
         {