I've got the same problem on my Mbox Pro running on a MacBook Pro OSX 10.8.3. I set up the Sound output to Mbox Pro (preferences). It works when I play 5.1 files in Twisted Wave but not in WwIse, only Left and Right channels seems to get out of WWise (Of course I choosed 5.1 Channel configuration in WWise Audio Tab). And If I try to use soundflower 64 ch it is the same, only the 2 first channels play sound . Do you have any idea ? I'm working on a big soccer event for Adidas and using WWise for the crowds would be awesome ! But it needs to be in 5.1 (as I recorded the source material in 5.0)
Thanks
Yohann