Nice looking truck. Try troubleshooting by isolating the lights and reflection cards in the scene, delete one and test render without it and see if it goes away, if not try the next. My guess would be that it's a diffuse reflection coming off one of those poly planes, I've had similar problems with light cards.

Also before deleting things, try turning off visible in refractions in the render stats for those planes the angle's strange so it might be that difficult to say what's what most of the time.