Not able to change password with passwd

[Nairolf Relsserp <airflow.2010@gmail.com>]

Hi,

recently I set up a new server using Debian testing. When I tried adding a new user a few days later, I noticed that it was impossible to set a password for the user.

The error-message ist "System error" together with the information that the password is unchanged.

root@fp:/home/airflow# adduser lorenz
Adding user `lorenz' ...
Adding new group `lorenz' (1001) ...
Adding new user `lorenz' (1001) with group `lorenz' ...
Creating home directory `/home/lorenz' ...
Copying files from `/etc/skel' ...
passwd: System error
passwd: password unchanged
Try again? [y/N] y
passwd: System error
passwd: password unchanged
Try again? [y/N] 
Changing the user information for lorenz
Enter the new value, or press ENTER for the default
    Full Name []: 
    Room Number []: 
    Work Phone []: 
    Home Phone []: 
    Other []: 
Is the information correct? [Y/n] 
root@fp:/home/airflow# 

Then I found out that it's impossible for none of the existing users to change their password, neither:

Here the output if the existing user "airflow" tries it himself:

airflow@fp:~$ passwd 
Changing password for airflow.
(current) UNIX password: 
passwd: System error
passwd: password unchanged

And also when root wants to set it for the same user:

root@fp:/home/airflow# passwd airflow
passwd: System error
passwd: password unchanged

I didn't find anything on the net. Any ideas?

Thanks,
Florian