...no site that she accesses with Explorer 9 will accept her e-mail address when this is requested.
Are you saying that a website that requires a username and password to log into is not recognising the log on details?
Back to basics; is your wife using the correct username and password? is the spelling correct? No extra dots where there shouldn't be?
Everything seems to point to a user input error. You could also try checking with the websites that you are using the correct login info.