Vivid - Login Loop, with upstart not

Hi
Well, I'm not sure if this is a bug or just a config issue. I installed the fingerprint utility after a quite recent vivid fresh install and it worked quite well, but two hours ago, I couldn't login properly. Even with the password the little icon just rotated. As I switched to TTY3, I couldn't login as well. Just a bunch of new status lines of byobu terrminal, generated every second or so.

After chosing the ubuntu with upstart version. I could login properl with no issues.

my system:
Toshiba Tecra AMD laptop, with proprietary grafics driver. bunch of recently installed software, and always up-to-date. I should mention that with the fglrx-update driver I only get in ca. 1 out of 5 logins after a start a normal screen (the other time it's shifted to right and sometimes shifted and horizontally pixel-linewise distorted, but at login suspend and unsuspend solves the issue).

Well, don't know what further information is needed (logs etc).

Many thanks for the advice if it's desired that I open bug...

cheers
sto