Well if that ain't gosh-derned spiffy
I've always felt that Douglas Adams laid out the best solution to the cause-and-effect messyness of time travel. He put forth that history can't be changed; everything fits together like a jigsaw puzzle and it's all taken into account. The only trouble left is figuring out the grammer to describe it all.

He might not be that wrong. Seems that quantum mechanics may rule out the "Grandfather paradox" all by itself, since quantum particles can behave both like particles and like waves.

Quantum theory allows time travel because nothing prevents the waves from going back in time. When [physicists Daniel] Greenberger and [Karl] Svozil analysed what happens when these component waves flow into the past, they found that the paradoxes implied by Einstein's equations never arise. Waves that travel back in time interfere destructively, thus preventing anything from happening differently from that which has already taken place (link). "If you travel into the past quantum mechanically, you would only see those alternatives consistent with the world you left behind you," says Greenberger.

It's totally bizarre, but then again most of quantum mechanics is. Of course, now there's no reason to be surprised if Scott Bakula shows up out of the blue in a dress and helps you out.  ¶ 6:34 p.m.