corrupt (mixed up) music files

Several of my music files appear to be corrupt.  Meaning a minute or so plays then suddenly the song switches to some other music file on the device.  Then that song plays for the remainder of the length of the first song (but then it cuts out when the first song was supposed to finish).  Anyone else have this problem?  The file sizes on the device are the same as the uncorrupted originals but the checksums are different of course.