Index: /trunk/src/VBox/VMM/VMMR3/CFGM.cpp
===================================================================
--- /trunk/src/VBox/VMM/VMMR3/CFGM.cpp	(revision 46790)
+++ /trunk/src/VBox/VMM/VMMR3/CFGM.cpp	(revision 46791)
@@ -1940,5 +1940,6 @@
             if (pNode->pParent)
                 pNode->pParent->pFirstChild = pNode->pNext;
-            else if (pNode == pNode->pVM->cfgm.s.pRoot) /* might be a different tree */
+            else if (   pNode->pVM                         /* might be a different tree */
+                     && pNode == pNode->pVM->cfgm.s.pRoot)
                 pNode->pVM->cfgm.s.pRoot = NULL;
         }
Index: /trunk/src/VBox/VMM/testcase/tstCFGM.cpp
===================================================================
--- /trunk/src/VBox/VMM/testcase/tstCFGM.cpp	(revision 46790)
+++ /trunk/src/VBox/VMM/testcase/tstCFGM.cpp	(revision 46791)
@@ -133,4 +133,5 @@
     RTTESTI_CHECK_RETV((pRoot = CFGMR3CreateTree(NULL)) != NULL);
     doGeneralTests(pRoot);
+    CFGMR3RemoveNode(pRoot);
 }