Subject: Can cncertainty in velocity cause potential velocities above c?

Take a proton, and accelerate it close to c, then measure it's position as 
accurately as possible. According to Heisenberg, the momentum then gains 
in uncertainty. The mass is known, since it is a known particle, implying 
the uncertainty is in velocity. Since the particle was previously close to 
c, the delta may bring the maximum potential velocity above c. This seems 
to imply that Einstein is wrong about c being the maximum possible 
velocity. How is this contradiction resolved?

Re: Can cncertainty in velocity cause potential velocities above c?