I have a new 27" 3.4GHz iMac and am confused by the sound. I am using an optical cable from the iMac to a multi-channel receiver. When I watch a DVD in OS X, I don't get DD5.1 sound from my receiver, I can only force DPL by pressing a button on the receiver. However, I do get DDD5.1 being automatically detected and decoded in my receiver when I use the same DVDs in my Bootcamp/Windows 7 partition! Can anyone explain to me what is going on? Thanks.