If you run IE7 and have tried Kontrollbase you may have noticed an infinite progress bar for the authentication. While login works on all other browsers, it was broken on IE7. The change has been committed to the repo and will be available in the next release. If you are inclined to edit one file here is the diff change. The file is system/application/controllers/login.php and the change is for line #68.

68c68
< $user_system_user_id = $this->session->userdata('user_system_user_id');
---
> $user_system_user_id = $this->phpsession->get('user_system_user_id');