Customized create user wizard not working

I have a CreateUserWizard I have customized to gather extra data.  I followed the examples at 4Guys and am still having problems.  It crashes whenever I call Membership.GetUser(_username), saying "Object reference not set to instance of object."

I am implementing this control in a CMS that handles multiple domains, so in the Creating_User handler I substitute in the username with the appropriate domain as per the CMS package's documetation.
The wizard is nested in a LoginView, so whenever existing users browse to their account pages they will not see the wizard.

I was under the impression that Membership.GetUser should be able to return the newly created user so long as it is in the CreatedUser event handler  
Can someone please tell me how to get the UserId of the newly created user to pass to my insert command?

private string _usernameAsEntered = ...