What about the DIGI.1 ghost?
I'm having a similar problem with the D550. I have a Samsung TV, but not one with ARC. I have connected my cable box (TiVo) to the D550 via an HDMI cable and then I have the TV connected to the D550. Audio and video work fine (as does Anynet+) when the D550 is on HDMI.1. However, the D550 will automatically switch to DIGI.1 (especially within the first minute after I power on my TV and soundbar). When the D550 switched to DIGI.1, I lose video as well. My guess is that the D550 thinks I have ARC since i have Anynet+ on and switches to DIGI.1. Does that sound possible?
One work-around I had was to connect my Tivo via optical cable to the D550 and then connect the video directly to the TV via HDMI. I then ran a "dummy HDMI" cable from the D550 to an unused HDMI port on my TV so I could still use Anynet+. This allowed me to control the volume (even when on DIGI.1) with my TV remote using Anynet+ and automatically turned off the D550 when I turned off the TV.
Any other suggestions?