Issue with low voice volume on 5.1 through SPDIF

For the life of me I cannot solve this problem. Here are my setup details;

Win 7 32bit
Realtek ALC889A
Media Player = Windows Media Center(player) and Total Media Theater
Latest Realtek HD driver r.239
Movies copied as .vob no conversion straight copy
Yamaha Receiver connect to PC via SPDIF

The problem is that anytime I play a movie with 5.1 all the sounds
perform perfectly except for the vocals. The vocals are barely audible.
The receiver is picking up 5.1 and playing it through all speakers properly.
It was working fine for about a month and then a few weeks ago it just stop playing correctly.

I have tried changing every setting possible in the sound card properties and
realteks HD manager. I have uninstalled the realtek driver and let the MS default HD driver install but ended up with the same issue. I have also reverted back to an older Realtek driver but still no solution. I have had Shark007 codecs installed (to play some other .mkvs ) but even after removing the codecs I still have a low voice volume issue.

Maybe I'm missing something simple but any help would be appreciated. I have been working on this for weeks!

Have you done this? http://www.sevenforums.com/sound-audio/21089-low-sound-volume.html#post234986

Don't forget about the Mic boost button.