Do you remember what happened in the movie? First, a scientist in India discovers that particles called neutrinos from a massive solar flare (explosion on the surface of the sun) are hitting the earth. These neutrinos supposedly act as microwave radiation, much like your microwave. What do they do? They start heating Earth's core. As a result of heating, Earth's north and south pole undergo a change in location. (Remember in the scene where a scientist said that the north Pole is now in Wisconsin?)  The movie showed this as causing huge earthquakes, enormous volcanoes, and killer tsunamis. As a result, billions of people died because they were unprepared for this.

Before we go further, it is worth talking about the "science" in the movie 2012.  As with many movies, there is a kernel of truth but the majority of what happens is not scientifically accurate.  For example, there are particles called neutrinos, but they hardly interact with matter at all and the vast majority of them pass right through the earth without being noticed.  They do not act like microwaves, and would not cause the core to heat up.  Microwaves are a form of electromagnetic radiation (ie, light) with a particular wavelength.  They cause water to heat up because of particular properties water has (the microwaves cause water molecules to rotate back and forth, which increases what is called the kinetic energy of the water, which in turn causes the water to heat up), but would not cause the core of the earth to heat up as portrayed in the movie.  As for the earth's magnetic field, it does change direction every ten thousand to one million years in a process called geomagnetic reversal.  This process is not fully understood, but is thought to involve the circulation of liquid metal in the earth's core.

Now, to answer your question: there is no evidence that the world will end in 2012.  The movie is meant to be entertainment, and while fun to watch it is not based on real science.  While neutrinos do exist and the earth's poles do change orientation, this has not happened in roughly 780,000 years and there is no reason to believe it will happen in 2012.

So don't worry about it! Keep on thinking and asking questions. It never hurts anybody!