strange totem problem
 

Hi ! It's my first post here, I hope some of you know a solution for this strange problem.
Basically the situation is the following. I have the latest version of Ubuntu linux. I have almost no problems playing movies with the totem player, except for one. When I play some movies(what is interesting only the movies which are ripped on 2 CDs) I hear all the sound except for the voice of the characters. I'm sure it's not because of the movies for I play them with all the sound using VLC or Mplayer for example. The thing is that I have some problems loading subtitles under these two and I prefer using Totem. I noticed something which may have nothing to do with this problem but when I start such a problem movie a few of the properties of my sound options are changed. I just don't know where exactly the problem is. Thanks for your help in advance!
Victor.

I know the problem is strange, but doesn't anybody know something. I believe there is something wrong with my audio codecs. I have a few installed but maybe more I needed ?