Well, I take a look at that question in a guest post I did for Another Cubs Blog. Basically, using t-tests, I came to the conclusion that -- while the Cubs have definitely been unlucky -- they do not seem to be cursed -- in the sense that their bad luck defies statistical explanation.
The chief obstacle the a World Series win on the north side is the "coin flip" nature of the playoffs. If the Cubs want to break the curse, they just need to reach the playoffs more often. (That sounds like John Madden all of the sudden.)
Read the full study here:
The Great Chicago Curse: A T-Test Exploration!