Learn from my misery.
If you are going to buy tickets online for more than one showing, Fandango has some sort "multiple transaction" thingy, where it tells you that you have already purchased tickets for this movie and asks you to confirm the second purchase.
Which is thoughful of them to protect you from your own idiocy, except not.
Seems there is a glitch in their matrix and it won't let you (meaning ME) click through on the "go ahead and buy the damn ticket already" option without sending you into some sort of infinite loop, thus making you unable to confirm that you want to purchase. You can cancel just fine, but who wants to do that?
If you have this problem, you need to log out (if you are signed up with a fandango account) and/or use a different credit card than the one you made your first purchase with.

Basically, it's a HUGE pain in the ass, and even though I have my "print at home" ticket (Aieee! Don't fold it over the barcode!!!), I'm going to be completely paranoid that something is going to go wrong and on Wednesday night, I'm going to be stuck in the arcade playing Dance! DANCE! Revolution for two and a half hours while everyone else is enjoying the movie.

Which would be good for my body, but very very bad for my soul....