I have found that MP3 does not order well, when the tracks are listed like (1,2,3,4) and it orders them like (1,10,11,12...19,2,3 etc), this error, when you look for the tags in freedb (or amazon) and you insert them, the program puts them in a wrong way.
This can be fixed by putting 0 in the numeration (01,02..10), but some people dislike doing it that way.
Screenshot: