I don't know the specifics about quantum entanglement, but any means of making information travel faster than light that can work reliably in two different inertial frames (thus communicating four different points, two not moving relative to each other in space in each) can be used to break causality or relativity. This is achieved by constructing a loop in which if the second pair of devices is used to disable the first you have a time paradox.

This is the clearest place explaining it I'm aware of, but I bookmarked this a while ago and maybe now some video or animation explains it better: http://www.theculture.org/rich/sharpblue/archives/000089.htm...