Yup, quantum mechanics messes quite a bit with our idea of cause and effect. I hadnt planned to bring this so early into this discussion, but now that you have brought it up ,we might as well discuss it now instead of later.
Lets go back to a quite simple version of the double slit experiment. We have our double slit, a monitor and 2 particle detectors. The particle detectors are installed a bit behind the double slit, so the particles have to go through the slits first and then through the detector.
As long as we have both slit open, and the detectors turned off we get our usual wave pattern. As soon as we turn the detectors on, to see through which slit the particle goes, suddenly we lose the wave pattern and get a particle pattern. So the particles go only though 1 slit. The big question is, how can the particle "know" when the detectors are turned on, and when not ? The cause (the detector) happens AFTER the effect (particle go through either slit when turned on etc.) Somehow the order of cause and effect is exchanged, the effect happens before the cause. That goes against anything we expect to happen here.

Since a post i just made in "who built the universe" deals with the accuracy of quantum mechanics, i thought i c+p it here, since it is also of interest for this thread :

Since quantum mechanics is mentioned so often, and some people doubted that quantum mechanics is really correct, i wanted to make a few remarks on the accuracy of quantum mechanics. If you predict the outcome of experiments with the formulas of quantum mechanics you get a phantastic accuracy. Here a few quotes about it :

QUOTE:"Quantum mechanics is the most successful and the strangest theory in the history of physics. It is the theory that allows us to build postage stamp size computers that do billions of calculations in a second and to build nuclear weapons. It is strange because, unlike all previous fundamental physical theories, it does not model what happens physically. It only models how probabilities change over time. Yet no previous theory has come remotely close to the accuracy that quantum mechanics is at times capable of."

QUOTE:" Quantum mechanics predicts the outcome of experiments with a discrepancy of only 1 part in 100 billion. That´s like measuring the circumference of the USA with a discrepancy smaller then the width of a human hair. No other formulas in science come even close to that, its several orders of magnitude better then any other formulas in any field of science"

QUOTE:" if quantum mechanics is indeed wrong its so damn good wrong that its better then most right formulas"

Quantum mechanics and the theories it spawned are no doubt some of the strangest theories in all of science. They are totally absurd, yet it looks like nature itself is really that absurd on quantum level. As feynman put it :" You cannot understand quantum mechanics, you can only learn to live with it"