But before you go to the manual, let me tell you this....its not a problem with XBMC, if you go view by albums in windows media player with your exact same music list it iwll do the same thing, you will even see maybe three of one....the problem is different sources of where you get your music from, your ripping it, you downloading it (not that anyone does that ), everyone has a different method of ripping and tagging.
So one person might tag the album name as "Eminem-encore" or one might tag its as just "Encore" saving the eminem part for artist. There are also variations like Encore [UK], or Encore (advanced) ect.....This may not be your problem, but I know it is a lot of peoples problems....hence the reason i sort my music by artist and not album.....hope that helps, and if thats not your problem then sorry for wasting your time
j_guzzler