I seem to have inadvertently broken the game by doing things in a completely different order to how you are supposed to, during the Caspian Sea / desert level. I'm now stuck in perma combat, some NPC's have started to levitate and on top of all that, I'm stuck in a canyon with no obvious route of escape. Shame, because I was enjoying it prior to this.
With regard to the mute protagonist - I've never understood the developers decision to make him silent during game play, especially considering the fact that you hear him speak during the load screens.