If you have the same title in different formats in your library (e.g. flac and Vorbis), or you have the same title in different quality or sample rate or bit resolution, the current default skin just shows you exact duplicates (if at all) of that one title. It is possible that you select one title from the library and actually play that one title multiple times (from different files)...
So I suggest to add the file type (ogg,mp3,flac, etc.), maybe the bit depth (8/16/24, etc.) and the sample rate (44kHz, 48kHz, etc.) to the default skin.