I had this issue with a large portion of my mp3's and found that they at some point got fuggered by windows media player's indexing bug. I have since set the directory on my server they are stored in to read only and created an uploads dir so the stupid thing can't do it again.. but basically I found out that they were reporting as starting at a different point than the beginning and had a length in the file header that was wrong.. MOST players that I've come across ignore all of this for the purpose of playback. OMplayer seems to take offense however.. heh
I'll see if i can find the app i used to clean mine up and see if it helps you out.