Index: /trunk/src/VBox/Devices/Audio/DevIchAc97.cpp
===================================================================
--- /trunk/src/VBox/Devices/Audio/DevIchAc97.cpp	(revision 238)
+++ /trunk/src/VBox/Devices/Audio/DevIchAc97.cpp	(revision 239)
@@ -1664,4 +1664,11 @@
     if (!pData->ac97.voice_mc)
         LogRel(("AC97: WARNING: Unable to open PCM MC!\n"));
+
+    if (!pData->ac97.voice_pi || !pData->ac97.voice_po || !pData->ac97.voice_mc)
+        VMSetRuntimeError(pDevIns->pDevHlp->pfnGetVM(pDevIns), false,
+                          N_("Some audio devices could not be opened. Guest applications "
+                             "generating audio output or depending on audio input may hang. "
+                             "Make sure your host audio device is working properly."),
+                          "HostAudioNotResponding");
 
     return VINF_SUCCESS;