OK, you've got two seperate issue here, it sounds like.

First: You're in the wrong config file. You want /home/user/.mlb/config not /home/user/.mplayer/config. The Latter is for mplayer itself, and hosts all of the default player settings for when you use mplayer to open a video or audio file. So if you go to the former file name, you should be able to add the audio_follow=sea and have it work. You'll also see your other info stored there (since thats why you can get the audio).

Second: I didn't know that people couldn't open the config dialog in this iteration. In previous iterations, it would hang for me if I opened it twice per launch, but I fixed that error and the config works fine for me. So what I need you to do is open mlbviewer, select the configure option of the menu, and when it doesn't load, quit. Then find the log file ("/home/user/.mlb/outputlog.txt") and either send it to me, or post the text after "setup_cfg" or anything else that isn't either a dictionary of the default settings or a 2 to 3 word line that looks like a function call. That error should help me figure out whats wrong for you.