Why are there duplicate songs on my iTouch?

My iTouch has duplicate songs from one album.

One title will have a grey background, and when it is selected shows the album artwork, and plays the song. The other title will have a white background, only show a music note, and will not play anything.

It is a pain, because when it gets to the "blank song" I get to hear dead airspace.

What has happened?

The unit is a iTouch model MD059LL/A, Version 6.1.6 (10B500).

Thank you for your help!

David