hi!
well you mentioned that you have all right audio codecs, but my answer to this is: remove all codec packs and sort of things… like K-lite codec pack and other codec packs, and when you have done that, go to divx:s website http://www.divx.com and download divxplayer, voila!!!
vegas will accept the file with divx players codecs.. and you will have the audio, but not if there are many channels, that want not work!!!
if it’s more channels we have to take another step but later….
hope it works!!!
//Michail
MNO Production.