I like the doomsday theories, be it notrodomas (I make no attempt at spelling that correctly) or mayan, it's all fun. That someone miscalculated numbers isn't really surprising-math IS a universal language, but it's also the most strictly ruled and defined language there is-without the same rulebook what you're calling a derivative is what the other guy is calling a Sloth's Toe and mistakes can happen in the translation.
As for doomsday cause their calendar ran out- well, they made REALLY long cyclical calendars, and someone called the Spaniards showed up when they weren't expecting it (NOONE EXPECTS THE SPANISH INQUISITION!) and didn't get a chance to lay out the next cycle. I agree that the Spanish inquisition can lead to doomsday if you don't expect them, but I don't cal forgetting to write out the next months grocery list a prediction of universal doomsday.
Good link though! (and I apologize for ignoring this thread the first 3 times it popped up under "new posts" for presuming it was a hockey thread since you started it)