The wave function represents all that can be known about a quantum system, but that usually means that we only know the energy. In the case of entanglement we know the energy but not the momentum (e.g. angular momentum) of its components. When one component of an entangled system (one spin up and one down) is measured the wave function collapses and we immediately know the spin of the other particle with a speed exceeding that of light. However, if we knew how the momentum of the quantum system was distributed to begin with we could describe the system without a need for measurement and entanglement would not be an issue. So based on the inability of quantum theory to specify momentum it seems to me that quantum theory is incomplete. And due to the uncertainty principle a complete theory is impossible.