In the TV Setup Menu on the Humax you have the option to turn Dolby Digital On or Off, this applies to the optical SPDIF output. I think it's on by default anyway. Turning it off means you get 2 channel PCM decoded from the Dolby, as it does with MPEG2 Audio.

Mark
G68, baby Genelecs, Humax Foxsat, Oppo+Vanity93, Toshiba HD-A35, Pioneer CLD-925 + Meridian 519, various other random bits and bobs
Got a black G08.2 you want to sell?