Thanks monks!
this is correct - the only way to combined the files was to completely re-encode each mp3 with audacity. I even tried using a MP3::Tag to strip away existing tags but it was not enough. The only way is to re-encode, then the joining works. After encoding it was just simply opening each of the files, binmode both filehandle, binmode output filehandle and writing it the new file.
thanks again.
AL
There is a command-line utility called mp3cat which you should be able to compile on most *nix systems. If you have to do this very often, it may be much faster than firing up a GUI program to re-encode the files.
Aaron B.
Available for small or large Perl jobs; see my home node.