If all of these programs give you trouble, it's because you have VBR (variable bitrate) audio. One thing you can do is extract just the audio, make it CBR (constant bitrate) and then apply THAT audio track to the original video source... you never need to reencode the video, and you shouldn't either. But VBR MP3 -> CBR MP3 usually won't hurt much, besides possibly file size. But again, variable bitrate mp3s are difficult to work with. Pretty sure Nandub or VirtualModDub will do it though. Give it a whirl.