I put this in Chatterbox but it may be better here, When I try to update my email address on the profile page, after I've put my new email address in twice, I get a message across the top saying the new email address does not match the one registered/ I feel I'm going round in circles.
I've changed mine a few times, including changing it back to one I'd registere on here before, without a problem.
If you have typed it exactly right both times and pressed SUBMIT and it's not worked then maybe you need to email the Ed.
One final thing to try- sign out of AB completely, then clear your cache ( internet options, delete history of pages visited, etc), wait a minute, then sign back in and try again