I have a Slingbox 500 which I used to connect with analog cables, but am now able to use with HDMI. (And I need to keep it this way, since my cable box won't stream dual, and my A/V receiver and everythign else is connected by HDMI).
My Slingbox is not decoding/downmixing the Dolby Digital stream from my cable box when streaming. I get video but no sound. I know this is the issue, because if I manually change the cable-box' audio output setting to "stereo", the sound appears instantly. This is awkward to do every time I want to stream though, and inconvenient since I want surround sound in my actual home.
The article below clearly states the Slingbox is supposed to downmix any multi-channel audio and stream it in stereo, but mine does not: