I had the exact same problem as you. Here's what I did to fix it.
1) Pasted link into web browser http://phobos.apple.com/accountSummary
2) It opens iTunes and displays that error message - Now in Internet Explorer, go to Tools-->Options & delete your cookies.
3) After having deleted cookies in Internet Explorer, click the little "Account" button near the top right corner in iTunes (it should have your account name in). This kinda does a refresh of the page in iTunes and this should fix it.
HTH