A slightly more retarded version of the apocalypse on 2012 that I've heard is that we're going to flip over the horizontal axis of the universe, and magnetism will stop working.
That sounds like someone misunderstanding the fact that we
may (by some reckoning) be overdue for a polar flip, where the Earth's magnetic poles swap over. (That's a summary. It's more complex, anyway.)
Depending on how fast it happens, we could be without a magnetosphere, and possibly unprotected from the ionised particles coming off of the Sun, in the solar wind, while it's 'off' (though if it just rotates around, should be no problem).
As geoological records only show it happening, this might happen very quickly or over a number decades (it's all "instant" by geological timescales). Expect migrating birds and hikers to get lost, unless they (the latter at least) are using GPS, in which case they might get away with it if the solar winds/other effects don't start to skuttle all the satelites. Also depends how much warning we have (we already keep track of the drift of the Magnetic North Pole, and occasionally someone says they think it's weakening) and thus whether we can prepare ourselves/our way of life against the situation.
Really a kind of Poor Man's Doomsday Scenario. Apart from the occasional navigation accident (and an increased risk of cancer?) it won't end the world, but Things Would Change (TM). All the really interesting solar flare stuff (i.e. Coronal Mass Ejections heading straight for the Earth) cause problems despite (because of?) the magnetic field, anyway and could fry the electricity grids and/or unshielded electronic devices on half the Earth's surface if the planet happened to wander directly in front of one. (Again, a summary, and not a little quoting the doomsayers while holding back on the obvious refutations to the argument.)