The strangest thing is there are no errors in any logs and service httpd configtest returns Syntax OK. I have tried killing all Apache processes and even rebooting server... ASL/Plesk work fine, but no standard http:80:443. It is a standard install with php-eaccelerator and php-suhosin all running fine before hand.
SOLUTION: Turned out to be a rouge character in /etc/httpd/conf.d/ssl.conf > SSLCipherSuite > HIGH was entered as HI GH. Not even looked at that file in an eon, but happy to be back up and running.