Index: libhb/work.c
===================================================================
--- libhb/work.c	(revision 1289)
+++ libhb/work.c	(working copy)
@@ -397,6 +397,15 @@
         int audioCodecsSupport6Ch =  ((audio->codec == HB_ACODEC_AC3 ||
             audio->codec == HB_ACODEC_DCA) && (job->acodec == HB_ACODEC_FAAC || job->acodec == HB_ACODEC_VORBIS));
 
+        if( audio->codec != HB_ACODEC_AC3 && job->audio_mixdowns[i] == HB_AMIXDOWN_AC3 )
+        {
+            /*
+             * Sanity check that we haven't asked for AC3 from a non AC3 track - drop this track
+             * to stereo to avoid a crash later.
+             */
+            job->audio_mixdowns[i] = HB_AMIXDOWN_STEREO;
+        }
+
         if( job->audio_mixdowns[i] != HB_AMIXDOWN_AC3 )
         {
         /* find out what the format of our source audio is */
Index: macosx/Controller.mm
===================================================================
--- macosx/Controller.mm	(revision 1289)
+++ macosx/Controller.mm	(working copy)
@@ -2929,7 +2929,7 @@
                 /* do we want to add a stereo option? */
                 /* offer stereo if we have a mono source and non-mono-supporting codecs, as otherwise we won't have a mixdown at all */
                 /* also offer stereo if we have a stereo-or-better source */
-                if ((!mp4AacAc3 && ((layout == HB_INPUT_CH_LAYOUT_MONO && audioCodecsSupportMono == 0) || layout >= HB_INPUT_CH_LAYOUT_STEREO))) {
+                if (((!mp4AacAc3 || audio->codec == HB_ACODEC_MPGA ||  audio->codec == HB_ACODEC_LPCM || audio->codec == HB_ACODEC_DCA) && ((layout == HB_INPUT_CH_LAYOUT_MONO && audioCodecsSupportMono == 0) || layout >= HB_INPUT_CH_LAYOUT_STEREO))) {
                     NSMenuItem *menuItem = [[mixdownPopUp menu] addItemWithTitle:
                         [NSString stringWithCString: hb_audio_mixdowns[1].human_readable_name]
                         action: NULL keyEquivalent: @""];