If you are trying to use email address as username in Django you have probably checked here
A comment that was previously true:
In Django 1.0 (since beta2) replace from django.core.validators import email_re with from django.forms.fields import email_re
is now erroneous. email_re has been moved back to django.core.validators.email_re. Now the original snippet is write again.
So, watch this when moving from Django 1.1.X to Django 1.2.
