^ I'm assuming you know what you are doing, since you've had the D2 for so long. Obviously there are settings mistakes that could cause this, and I'm assuming you've checked to make sure, e.g., the Setup > Source Setup you are using actually specifies HDMI Digital as the source of its audio. If you've not checked this, then that's the place to start. It is quite easy to screw things up. For example, if you changed the Source Setup to use Component Video as an experiment, that has the side effect of SWITCHING THE AUDIO AS WELL since obviously you can't have HDMI audio coming in on Component Video.
Similarly, try running HDMI from the cable box direct to an HDMI TV to make sure you haven't somehow altered the settings in the HDMI cable box to disable HDMI Audio output altogether.
So ignoring settings mistakes, that leaves settings corruption, firmware corruption, or a hardware failure.
Jot down your settings, then do a Reload Factory Defaults on the D2. Make only the minimum necessary setting changes to test if the problem still exists.
If it does, Reload Factory Defaults again, then re-install the v1.33 firmware in the D2. Once again, make the minimum necessary settings changes to see if the problem still exists.
If you've still got a problem, call Anthem Tech Support and they can help you diagnose this further.