in V6? I did the "RealTek Audio" 6-ch. test, and I hear each spkr fust fine. But when I go into V6, and I turn on 5.1 ss in the project properties for audio, I'll access an audio track, click/drag the diamond representing the audio spectrum, and all I get is stereo. I tried re-booting. Same thing.
Go to Preferences > Audio Device and adjust things to where they should be (it's different for everybody, or at least me and the two different audio cards I've used for surround in Vegas).
In my case (Santa Cruz Turtle Beach surround card) only the DirectSound in the Audio Device tab will properly put the surround channels in back. All the other choices maps the rears to the fronts.
Also, prior to V7, choosing the DirectSound option would put the audio way out of sync with the video, making it more cumbersome to edit (do some things in DirectSound, do most everything else in Soundmapper). In V7, the sync seems to be okay (so far).
i've never had a problem with out of sync with direct sound. I've had problems with using the JKL keys (vegas 4 would crash for me) but i don't belive to have that problem in V6 (i have OTHER problems. :) )