Something shorted on that side. Check both the front and rear bulb on that side. It could be something as simple as the back of the bulb is no longer making contat with the lead. It's more likely a ground issue on that side, if both bulbs are good. HD Dude can probably give you more specific direction.....being the wiring wizard that he is.
Not to be picky, JC, but I'm thinking more along the lines of an open in the circuit.... Try turning on the right side blinkers, and then hit the left switch... If it's an open out in the circuit, it will cancel the right lights, but not turn on the left side. (at that point look for opens on the grounds, at the bulbs, at the housings...etc) If it does Nothing, then I would look for junk on the contacts withing the left side switch or a pinched wire on/in the bars. If both of those options go no-joy, I would drop in the dealers lap, 'cuz it's most likely the module, and should be covered under warrantee. (Not that the others wouldn't be, but I would rather do what I can so the orangutan at the dealer doesn't screw up any more chrome and paint than needed...)