OK, I just f*cked up testing, used the HDMI of a device that was connected to my AMP via Coax digital audio cable, so no sound was pretty normal
I've nailed it down to upstreaming Linux versions, somewhere between stock 3.0.31 and 3.0.67 sound stops working.
That's a good thing, now I have something to work on
JP.
EDIT : Narrowed down between 3.0.40 and 3.0.67 !