same problem , server mother board, ud5, and same OS version from MSDNAA and yeah audio feed back works when doing it with realtek manager, i send gigabyte a support ticket and they replied . with this
Thank you for your kindly mail and inquiry. Since Windows 8 is not officially launched now, we cannot guarantee it can work properly with our product. After we test the drivers with Windows 8, we will release them on our website as soon as possible.
If you still have any further question or suggestion about our products/service, please do not hesitate to contact us. We will try our best to help you resolve the problem ASAP.
Regards,
GIGABYTE
i just couldnt get this working i even posted the problem in MSDN web site
http://social.technet.microsoft.com/Forums/en-US/w8itprohardware/thread/aeab61e0-745d-46b9-84c6-c784e14ecb88some said it was a problem with hyper V, how ever i didn't enable hyper V so that's no help for me,
gigabyte really should do some thing about this, they most certainly would have received windows 8 way way before we got the copy so no excuse saying its not released yet.
since i couldnt get this working i have switched back to windows 7 for now.