I'd agree that the most likely cause of this effect is speaker phasing, but it's also possible that you are getting an acoustic anomaly in your listening room. Years ago, the audio club that I attended met in a local church that has an oddly shaped room with rather odd acoustics (probably due to room shape). The club's speakers were Acoustat 8's (electrostatics), and with certain recordings the left channel seemed to be coming from the left rear corner of the room. If you are only getting the "imaging from behind your head" phenomenon with this single recording, I'd attribute it to the a phasing problem on the recording. If it occurs with more than one recording, then you might try some room treatment, or slightly changing the position(s) of the speakers.