Why can I not update my phone?

I want to update my phone to the newest 6 iOS version but for some unknown reason, iTunes does not want to seem to work properly. Every time I try to update, it give me this message-

"The iPhone cannot be updated at this time because the iPhone software update server could not be contacted or is temporarily unavailable."

My phone is a 4s, I run this iTunes on a Windows 7 Laptop, and iTunes was just updated yesterday.

My phone is not jailbroken, so that should not be a problem.

Any fixes? I have gone into the hosts file several times to see if that could fix it, but with no effect.