Run
MP3Test and it will show you which mp3's have errors and what type of errors. The program is a free trial and when 30 days are up you can still use it but with a nag screen.
Most errors are from garbage at the front or the end of the file. You can usually fix them with
mpTrim, however the free version only lets you edit one file at a time.
If you have a lot of files to fix try
MP3 Repair Tool.