Please write a brief mail to bugs@ableton.com about the problem, and attach the file to the mail. This error occurs occasionally, and depends on which program was used to create the audio file. You can use an external audio editor to open the files that Live thinks are corrupt, and then re-save them (under another name if you want to avoid confusion) with the program's Save-As command. When you load these files into Live again, the problem should be solved.