PAM stands for Pluggable Authentication Modules
"Since the beginnings of UNIX, authenticating a user has been accomplished via the user entering a password and the system checking if the entered password corresponds to the encrypted official password that is stored in /etc/passwd.".
See more here
PAM related configuration files can be found under /etc/pam.d directory. Check this
So confliction could be between two names used for login i.e. in GUI based login screen that appears when you login into your system. Can you once share a screenshot of error, plus /etc/pam.conf output.