...okay, reboot, and then try it again.
Lastly; I'd suggest asking a very dear friend to log into iTunes for you, from their computer. Unless of course you have two computers at home. Or even try it from your work computer, if that is an option.
In addition, you might have to post a screen shot so we can see. Of course, omit the email address (security measure).
PS: remember to deactivate it on that 'other' computer once you're finished testing.