I don't how competent am I, but what I would personally do is try to convert the files to say, wav:

1. Try soundkonverter (sudo apt-get install soundkonverter): I use daily, great converter from/into most audio formats.

2. Then, there is the Perl Audio Converter who offers even more options (sudo apt-get install pacpl). It's a terminal/perl based app, but offers even greater range of audio formats (and maybe different libraries?).

Finally, open it in audacity? I had a few problem with some audio files in the past, and opening them in Audacity would 'clear' all errors.

Hope this helps