This is a quick one, not a lot of information out there on it. If for some reason you find that your pubcookie setup isn't working because when you hit login and you login successfull your browser starts wigging out and looping back and forth between the login page and login successful page ... it is most likely caused by the wrong time set on your server. Pubcookie requires your server to be within 60 seconds of the pubcookie authentication server. Otherwise it gets stuck in a loop. To best handle this, setup and install NTP.
yum install ntp (this installs ntp if its not already)
chkconfig ntpd on (adds daemon to startup)
service ntpd start (this starts service)
if you need to modify the ntp server list, go to /etc/ntp.conf
 
Once your time is set, restart apache (service httpd restart) and it should work properly again.
REMEMBER, ntp will not jump your clock into sync as it could miss scheduled tasks. So it slowly dials you in.