Index: /trunk/src/VBox/Devices/Audio/DevIchAc97.cpp
===================================================================
--- /trunk/src/VBox/Devices/Audio/DevIchAc97.cpp	(revision 68411)
+++ /trunk/src/VBox/Devices/Audio/DevIchAc97.cpp	(revision 68412)
@@ -1219,9 +1219,14 @@
 static void ichac97StreamUpdate(PAC97STATE pThis, PAC97STREAM pStream, bool fInTimer)
 {
+    ichac97StreamLock(pStream);
+
     PAUDMIXSINK pSink = ichac97IndexToSink(pThis, pStream->u8SD);
     AssertPtr(pSink);
 
     if (!AudioMixerSinkIsActive(pSink)) /* No sink available? Bail out. */
+    {
+        ichac97StreamUnlock(pStream);
         return;
+    }
 
     int rc2;
@@ -1335,4 +1340,6 @@
 #endif
     }
+
+    ichac97StreamUnlock(pStream);
 }