What email service are you using (don't post the actual account name, just the company that provides the email address)?
Because when you enter an email address into your account, if Dakka tries to send you an email and it bounces back from your email account (because that email service is identifying our emails as spam, for example), then Dakka will automatically delete your email address from your account and replace it with your username. This is done as a protection for us, because if our email server gets reported too many times as sending out spam (just because an email service or particular email account is considering all our emails spam for whatever reason), then our email provider will drop us.
Actually, probably a better idea would be for you to email me directly @:
webmaster@dakkadakka.com from the email address you're trying to use. Just make sure to put your Dakka account name somewhere in the email so I know it is you.