Problems changing root password

[Javier Diaz]

Hi!

I have a problem when i try to change root password in a Red Hat Linux
Advanced Server release 2.1AS. I have change root passwords every months but
now I get an error when I going to change it:

New password:
Re-enter new password:
passwd: Authentication failure


If I see /var/log/messages:

Jun  8 12:42:40 passwd.prepwplus: PWplus: From Login=javi, Uid=0(root),
User=root, Password checks passed.

Jun  8 12:42:40 passwd(pam_unix)[24188]: authentication failure;
logname=javi uid=0 euid=0 tty= ruser= rhost=  user=root

Jun  8 12:42:40 passwd(pam_unix)[24188]: user password changed by another
process


Which could be the problem and how could I solve it?

Thanks,
Javier