We are running on CentOS 5.3 32bit and did an upgrade from 2.4.8 to 3.0.1. Everything went fine, except we were unable to access the wp-admin portion of our site. We are running Apache, memcached and varnish. We shut down Varnish but still no access to the admin pages. We rolled back to 2.8.4 and looked at all the logs (/var/log, and root/logs) and found nothing wrong. How can we troubleshoot this?
San Diego, California