Hi aeroguy,
a very interesting problem...
I had a similar situation with my pc at first....
there were so many places to check...
the dvd player used...and it's decoding capabilities...
the audio settings...from audio or video cards plus others...
is the player on your mac DTS compatible ?
Do you get Dolby Digital ?
not 2.0 but the sought after 3.2.1
is your Mac down-mixing into two channel ?
(setting my pc to ''passthrough'' all audio fixed my problem)...
please let us know how your situation evolves...
I'm curious....