Everyone asks for their username and password at some point, so this gives me a few extra minutes to play GTA4 ;)
Just enter your email adress here and press "Gimme My Password!", and your username will be emailed to you. Here's the fine print:
1) You must use the email address listed in your profile, that's the only way I have to know who you are.
2) You must have access to that email address, or you'll never get it. Sorry, can't help that.
3) You can put someone else's email address in there, but then they'll get their username and password.