FaceTime isn't working on iPhone 4S?

I've been using FaceTime ever since I got the phone and it worked perfectly fine, but in the past 3 days, everytime I try to FaceTime my friend, it stays on 'connecting… ' For a few minutes then it says "call failed".It's on iOS 6 at the moment. How can I get it to work again?

I'd the same problem and i solved it by restoring my phone.