Duff-Man says....Open up one or two of the files in an audio editor - freeware like Audacity will do the trick. See if there is "blank" space at the end of the files...it's quite common with some mp3 encoders to have this (bad!)....oh yeah!
are you playing it back in your mac??
some cd players (theory, not sure) may automatically put 2 secs between tracks. you might want to try it in different players...