Some important updates are at the bottom of this article.
OK folks, nothing to see here.
I talked with my buddy Seth Shostak, who is a Senior SETI astronomer, and he told me that this whole alien signal thing is a big misunderstanding on the part of the KTVU reporter.
Basically, Dan Wertheimer, a radio astronomer who is affiliated with SETI,detected a pulse from space told the reporter about a signal that had been detected from space. The source is certainly extragalactic, and is most likely some sort of natural event. It's unclear exactly what kind of event, but there is a long list of things it could be. Aliens phoning us is pretty far down that list. But since Dan does do some SETI work, the reporter just botched things up a bit and misattributed the source. The news article reads oddly, like he took a mishmash of topics and wrote them all up into one article, so this misunderstanding doesn't surprise me much.
The signal was detected quite some time ago, and had it been alien, believe me you would have heard from the folks at SETI!
So chalk this one up as yet another in a long line of false alarms. Sorry to burst the ET bubble.
UPDATE (18:45 Mountain time):
1) The original news article -- shocker -- has been pulled off the KTVU site. However, someone should tell KTVU that there exists this thing called Google, and they sometimes cache web pages. I also took a screen capture of the meat of the article and uploaded it to my Flickr page.
2) I just talked to Dan Wertheimer, the astronomer quoted in the article. He told me that the original interview was about sending signals into space (so-called "active SETI") as opposed to just listening for aliens. After the interview, he talked to the reporter about some of the astronomy he does, including looking at what are called radio transients: bursts of radio waves that are seen once and never repeat. These may come from one-off events like colliding neutron stars, exploding stars, and so on. Somehow, in the article the reporter mixed up the observation of the transient signals with detecting a signal from E.T. Worse -- if that's possible -- the observations of the transients weren't from Arecibo, and they weren't from Wertheimer. It was another astronomer altogether, observing with the giant Parkes radio dish in Australia.
So basically, the news article is utterly wrong about everything it discussed concerning the signal. Wow.