http://www.pbs.org/wgbh/nova/physics/blog/author/fwilczek/ Frank Wilczek: "As we've seen, if a and b are space-like separated, then either can come before the other, according to different moving observers. So it is natural to ask: If a third event, c, is space-like separated with respect to both a and b, can all possible time-orderings, or "chronologies," of a, b, c be achieved? The answer, perhaps surprisingly, is No. We can see why in Figures 5 and 6. Right-moving observers, who use up-sloping lines of constant time, similar to the lines of constant t2 in Figure 2, will see b come before both a and c (Figure 5). But c may come either after or before a, depending on how steep the slope is. Similarly, according to left-moving observers (Figure 6), a will always come before b and c, but the order of b and c varies. The bottom line: c never comes first, but other than that all time-orderings are possible. These exercises in special relativity are entertaining in themselves, but there are also serious issues in play. They arise when we combine special relativity with quantum mechanics. Two distinct kinds of difficulties arise as we attempt to combine those two great theories..."
One does not try to combine "two great theories". Rather, one tries to combine the sane concept of time used in quantum mechanics and the insane concept of time offered by special relativity. The situation is more than schizophrenic so clever Einsteinians leave the sinking ship without any hesitation:
http://www.edge.org/q2008/q08_5.html John Baez: "On the one hand we have the Standard Model, which tries to explain all the forces except gravity, and takes quantum mechanics into account. On the other hand we have General Relativity, which tries to explain gravity, and does not take quantum mechanics into account. Both theories seem to be more or less on the right track but until we somehow fit them together, or completely discard one or both, OUR PICTURE OF THE WORLD WILL BE DEEPLY SCHIZOPHRENIC. (...) So, I eventually decided to quit working on quantum gravity."