The SA8300HD configures the audio output of the HDMI port ONCE the first time it is hooked up to a device. So if you had it hooked up to your TV then moved it to your Home Theater the HDMI audio output my not be set properly.

Here's a link to the user's manual I pulled that info out of. It also explains how toget in and manually reset the HDMI port.
SA8300 User Manual

Hope this helps...