It frustrates me that Apple doesn't update it's System Status page when these things happen. They're supposed to, but most of the time when there are obvious glitches (like now) they pretend everything is fine and dandy and it's all in the green. What's the point of implementing these systems if you don't use them correctly?
Apple aren't the only company guilty of this, it's prevalent across the industry.
I know this is an old thread, but I had this problem, and I fixed it by simply adding a new Network location in the System Preferences. I can't figure out why it should matter, since all of the settings are the same (I checked), but hey, I'm not complaining.