Check to see if the reticle is square with the turrets. You can do this with a boresighter (a good one with a grid) or by aiming at the edge of a building, lining up the reticle with the edge of the building and cranking the turret up while holding the rifle solidly. The reticle should track down the edge of the building, not veering left or right.
If the two are square, remount the scope and/or the level...level.
If not, send the scope back to Leupold and they'll hopefully fix it.