If you are using a Mac computer, try this solution from user wingv that I found in another thread:
Type sudo su
Then enter your password and hit enter
Type vi /etc/hosts
Move your cursor with the down arrow to the line that has gs.apple.com without a # at the beginning of the line.
Move cursor to the beginning of that line.
Type i# then press the esc key.
Now you can quit out of the terminal application. This likely is a problem caused by Tiny Umbrella denying itunes communicating with the apple servers.