Related is the assumption that witches of the time--in whatever form they did or didn't exist--could actually cast such a curse. Again, we have no way of proving this (or knowing that there were witches present, or that Shakespeare got his info from witches, or whatever story you'd likeone wants to believe. Very few of these earlier tales can be cited, as Skeptoid explains above). There's a good question here on Skeptics about black magic that concludes it's not real, but again for this kind of claim, it's nearly impossible to "really" disprove it since you'reone is disproving not-phenomona with more not-phenomena.
When a rumor goes on this long, as Lagerbaer said in the comments, you've gotit creates a pretty powerful sell-fulfilling prophecy. People are going to look in one place for problems, ignore them elsewhere, and cry loudly when they arise. What really needs to be asked is, "Are these events, true or false, atypical?" We're talking about one of the most popular plays/stories in the world, one that's been performed for over 400 years now. How many thousands, hundreds of thousands of performances is that? Google "Macbeth performances" and you getfind almost nine million hits. Of course they're not all unique or useful, but this is an exercise in massive scale. Let's say Macbeth is only performed once per year. Your source document has 27 instances noted, but even 27 terrible incidents out of 400 is just 6.75%. Is the margin for accidents in stage performances so drastically less than 6.75% worldwide that this deserves to be considered bad luck?
Furthermore, in looking for a curse, you find yourselfone finds oneself attaching mishaps to an event that would otherwise have no relevant place in that event's context (and are certainly in no way provably causal). England was hit with an extremely violent storm on the day production opened. So? What other billions of actions were taken that day, and why didn't they cause the storm? Lincoln was reading Macbeth a week before he was killed... and? That's not even talking about stage productions, that's implying any one of us could be stricken down for a 9th grade reading assignment.