 2. Single Blind Flexible Dose Nabilone Treatment Phase This is a 4 week 28 day treatment period when subjects will take nabilone in a single-blind fashion, at a dose of 1-4 mg per day. All subjects will start with nabilone 0.5 mg po bid 1 mg daily for at least 4 days, and then their study medication will be assessed and adjusted upwards, or downwards, as needed to achieve optimal NeP relief as well as side effect tolerability. Dosing adjustments will occur at a maximum of once weekly, with the maximum dose of 4 mg per day preventing any further increase in dose, and a minimum dose of 0.5 mg per day preventing any further decrease in dose. At the end of this single-blind phase, all subjects who are deemed a responder those who experience a 30 reduction in weekly mean pain score will be randomized to the double-blind phase. Those subjects who are not a responder will enter the taper phase of the study, with end of treatment assessments performed. Those patients receiving a dose of 0.5 mg daily will receive a single capsule of 0.5 mg at qhs only. In order to prevent potential unmasking, those patients who are intolerant of placebo will also have their placebo dose reduced from 2 capsules daily to one capsule daily. 