Some songs don't have sound!

I used MP3Gain Express to level the sound level of all my songs to 87 dB. Then later I find out that almost half of my songs don't have sound! The progress bar moves but there's just no sound output. Sometimes for some songs which were like this, when I scrubbed the progress bar, there would be some sound for a second or two in some parts of the song but it would be garbled. After syncing to my iPods, the same problem is seen in the iDevices. There's just no sound! I scanned the system for any viruses using iAntivirus but there weren't any.

Any way to restore the sound in them WITHOUT using iTunes Match and the likes?

Using 10.8.3 OS X and iTunes 11.0.2