Simpletest, User login fails.

With a clean drupal 6 (simpletest patched) install and email_registration, launching tests fails starting from login of registred user (line 45 of email_registration.test).

Cause : After user registration, user is logged in and access to user/register is forbidden.

Adding $this->durpalLogout(); line 40 (just after $this->dupalPost()) fixes the problem for me.