Has anything happened as a result of all this?
I have started trialling AB, and have run across a similar situation very quickly.
I am using Input Director as my KVM (having tried several others and found them very similar. My main reason for choosing ID is that it is very simple to see the current arrangement of master and slave via the icon colours in the tray).
I just re-installed AB, for reasons which aren't relevant, and played a couple of tracks of music as a test.
The music played well on the target PC.
But when I played another track, it 'gurgled'.
This continued each time I started a new track.
I rebooted the source PC and the problem continued.
At that point I found this thread.
I changed the Passcode on the target PC (to the same value that it already had), and played another track.
Voila! The music was clear.
I'm using the trial software of AB downloaded within the last few days.
I will probably buy if I'm convinced it's been fixed.