Cannot connect to iTunes Store: error (-3212).

When I attempt to open the iTunes Store, I get a blank iTunes page with a pop-up error message: "iTunes could not connect to the iTunes Store. An unknown error occured (-3212). - Make sure your network connection is active and try again."

Obviously I've double checked my network, and then additionally looked through similar questions all over the Apple Support Communities, but couldn't find a solution. I'm entirely out of ideas; what do I do?