[Dovecot] dovecot(pam_unix)[13823]: authentication failure; logname= uid=0 euid=0 tty= ruser= rhost

[Donald Gunn]

I installed Dovecot on our FC3 sendmail server and get this from our 
Dallas office.

dovecot(pam_unix)[13823]: authentication failure; logname= uid=0 euid=0 
tty= ruser= rhost

Only one user can get mail (pop3 or imap). All local users work fine.
I ended upgoing back to UW and all works fine.
What should I look for?

Thanks