After installing PAM (0.80) and re-installing shadow (4.0.10) to use PAM, a strange error occured when testing the login in a new shell:
[SOLUTION]configuration error - unknown item ´NOLOGIN_STR´ (notifty administrator)
Edit your /etc/login.defs and search for NOLOGIN_STR. there you will see a comment saying that this flag was ripped out by a programmer.
So simply comment it out.