There is a mandatory dashboard update for the Xbox 360 out today that fixes the HDMI sound issues that some people have been having. Coincidentally, this update will also alleviate the problems we told you about last month after a few people installed a beta version of the dashboard update.
The problem, which popped up following the November 19 launch of the New Xbox Experience, left some Xbox 360 users without sound on certain HDMI-connected displays. Prior to the NXE, these devices properly outputted Xbox 360 HDMI audio. Xbox 360 users will be prompted to download the update upon signing into Xbox Live.
HDMI worked fine with sound on my new box before the update. My old box doesn't even have HDMI so yeah...not sure what the problem here was. I guess the problem was on the other device's end (TV's not accepting the new signal).
Xbox 360 Dashboard Update Fixes HDMI Sound 
Linear Mode
