Try the "Forgot Password" thingy at www.passport.net

I haven't actually run it but it might be something to try.  It's under Account Services on the above page.

EDIT: Of course once you run it the current password will be lost in favor of the newly generated one.  If you can't get your hands on the new one then you might be worse off.  I really don't know how that lost password system works however.