The correct protocol for electronic mail is all lower case letters in the address.

http://en.wikipedia.org/wiki/Email_address#Valid_email_addresses

Do you mean your name in a login form?

Make sure that you haven't saved multiple (uppercase, lowercase) versions of that name and password.

Remove saved Password(s):

• Tools > Options > Security: Passwords: "Saved Passwords" > "Show Passwords"

If you want to remove saved form data from a drop down list then use these steps:

1. Click the (empty) input field on the web page to open the drop down list
2. Highlight an entry in the drop down list
3. Press the Delete key (on Mac: Shift+Delete) to remove it.