It turns out I have fixed it (and potentially found the problem).
I use a 5.1 speaker system, the problem I found was that voices in cutscenes only play out of the middle speaker, which is the softest speaker, and the music/sound effects, play out of the side speakers, the loudest ones. I have a button on my setup that fakes stereo sound (funnels all sound to come out of the 2 front side speakers). This button didn't work for me.
But what I did do was go into my audio settings and change my speakers default to stereo (windows 7, control panel -> sound -> right click speakers or what ever you use -> configure speakers -> stereo), and now voices work fine. Sucks that I have to lose surround sound though.
Hope this helps!