Index: /trunk/src/VBox/Main/src-client/DrvAudioVRDE.cpp
===================================================================
--- /trunk/src/VBox/Main/src-client/DrvAudioVRDE.cpp	(revision 55158)
+++ /trunk/src/VBox/Main/src-client/DrvAudioVRDE.cpp	(revision 55159)
@@ -411,4 +411,7 @@
 {
     LogFlowThisFunc(("fEnable=%RTbool, uFlags=0x%x\n", fEnable, uFlags));
+
+    if (mpDrv == NULL)
+        return VERR_INVALID_STATE;
 
     mpDrv->fEnabled = fEnable;