Do you know what kind of files they're supposed to be? Usually if they show the Unix Executable icon, it just means that OS X doesn't know what kind of file they really are. Perhaps you got them from the Internet and there's no ".mp3" or ".aif" on the end. So the OS just guesses and says they're Unix Executable files.
If that's the case, just add the ".mp3" extension to the end of the file name and they should come in fine.
A lot of my mp3 got turned into unix executable files. I went from over 9 thousand songs to just over 5 thousand. I understand that all I got to do is add the mp3 extention but that's to many to do manually. Any ideas on an automated way of fixing this?
I've noticed that a lot of these messed up files were ripped in iTunes on my old Powerbook G3 years ago. Back then iTunes was Mac only so maybe that's why the extension wasn't added.
Lesson learned, never dump mp3 files directly into your iTunes folder. Just use the import button instead (or at least at first).