Change a user password.

I’m having problems changing a user password. I don’t seem to have the rights to do it. I can do almost everybody else, except for about 10 users. I did’nt create them, the current NW Admin did. I do have the rights to change others, but not thesefew. What I’m I missing ? I’m a trustee of the user object. I also noticed that if I log in as Admin or Supervisor, they can’t do it either. The only one person can do it is the current Admin.

Thanks