Kenmac, thanks for the reply - I might just get the cable for the YPbPr route as well, it's just too frustrating. With L-R you mean AV4, not the Camera connection behind that small door, right? Anyway, when watching picture on the BV7 via ATV, I get sound from the ATV, just not into BV7, but a seperate (active) speaker. That must mean that ATV indeed puts out sound while having picture out through HDMI.
Dan, thanks for the link. However, I would hate putting another box next to my new beauty, so I hope there will be another solution. Especially since I am so close -- after all, there is a picture.
Btw, sorry for writing "I tried EVERYTHING", did not want to discourage any other ideas givers.... ;-)