During a hand-launch, the torque effects of the engine are large compared to the aerodynamic forces of the tail and wing, so the plane rolls to the left. At a recent combat contest, we were launching with a pretty sizeable tailwind, and almost all the scale planes went left on launch. All of my scale launches were knife-edge. I'm pretty sure the wing wasn't really stalled (it wasn't rolling like I see when I do snap-roll), but there wasn't enough air over the surfaces to keep the plane from doing whatever it pleased for the first few heartbeats.

That said, did you check your lateral balance? I find that really messes with my combat planes ALOT.