I have the lack of sound problem with the Gehn installation on my new laptop.
Edited, 1 September 2014 - no I don't have the lack of sound - everything is fine today! Mysterious! But great!
Later in the thread you linked to, Jamie, is the following:
Tsar Hoikas wrote:Hi all, with Gehn 20, we updated a lot of our build tools. The component we were using to play audio was unavailable when we did this rebuild, so we used an alternative that appears to suffer from problems like this. I checked the other day and the old audio component was available again, so I will switch us back to the old, working component with the next Gehn release.
So it should be fixed soon-ish....
Edited, 1 Sept - it's already fixed - for me at any rate.