We’ve been asking around, and we have been downloading driver after driver and swapping sound cards all day long to no avail. Vista’s digital audio support is completely broken in this latest build. To be fair, it is not a CTP, but on the other hand, besides the lack of digital audio support on Microsoft Windows Vista Build 5342, it seems that the audio stack is exactly the same as that of 5308.
These comments are not made on whim nor are they fallacies in induction, NeoSmart Technologies carried out the most extensive review and troubleshooting guide for both digital and analog audio on 5308 (February CTP) which can be seen here.