This happens when files get shared allot and partial files are glued back together in bad clients .
Altough the file plays normal some programs like burning apps may complain .
Use a program specialized for these problems .
You can find this kind of programs in those huge download sites outthere .

BTW it says MPEG files and not MP3 because MP3 is based on MPEG .
MP3 stands for MPEG layer 3 compression .
You also have layer 1 and 2 wich are MP1 and MP2 files .