This is a bit more in depth information on this detection.  Only a few of these unusual radio signals have ever been found:

There is something strange in the cosmic neighbourhood. An unknown object in the nearby galaxy M82 has started sending out radio waves, and the emission does not look like anything seen anywhere in the universe before.

“We don’t know what it is,” says co-discoverer Tom Muxlow of Jodrell Bank Centre for Astrophysics near Macclesfield, UK.

The thing appeared in May last year, while Muxlow and his colleagues were monitoring an unrelated stellar explosion in M82 using the MERLIN network of radio telescopes in the UK. A bright spot of radio emission emerged over only a few days, quite rapidly in astronomical terms.

What do you think this could be from?  Apparently it does not fit the pattern of those that come from supernovae typically.

It certainly does not fit the pattern of radio emissions from supernovae: they usually get brighter over a few weeks and then fade away over months, with the spectrum of the radiation changing all the while. The new source has hardly changed in brightness over the course of a year, and its spectrum is steady.

If they ever do figure out what is sending these signals, it will likely either be indiciative of intelligent civilizations or perhaps astronomical phenomena that we have yet to understand.

thanks to newscientist.com for the great info