I get that error occasionally as well, a bunch of redirects to another redirect and what not. After you’ve entered the username and password info, try to go to a direct page within admin interface, like <b>/wp-admin/templates.php</b> or <b>/wp-admin/link-manager.php</b>. It seems that these links always work, while going to <b>/wp-admin</b> seems to engage some sort of redirect logic.