I have been having problems with some tracks not playing for quite some time, part of the problem seem to be related the way Spotify is managing their back end. Here is the proof:
http://open.spotify.com/track/454PvA7LkC77oZRwPqcdP6 (Track=Central Plan Artist=Carbon Based Lifeforms)
Exat same track Working:
http://open.spotify.com/track/7scMyDru0x1khrfW3WbKnj (Track=Central Plan Artist=Carbon Based Lifeforms)
This is the fifth or sixth time, I noticed the same issue. For a paid customer who have been using the system for many years, it is kind of dissapointing to see that Spotify is having problem staying organized.