I found the solution a few hours ago here
http://en.gentoo-wiki.com/wiki/Systemd#PAM_support:_su.2C_sudo.2C_screen...
. Now everything is fine :)

About the packages you mentioned, you've ran 'equery uses pambase polkit
udisks upower', and none of them has the userflag systemd. Anyway, systemd
is globally set on my system, and it is good to know I can disable
consolekit. I'll try it right now.

Thank you,

-- 
Joćo de Matos
Linux User #461527