try to use this way to start Apache:
# /etc/init.d/httpd start
In case if attempt will be failed, you can check /var/log/messages and /etc/httpd/logs/error_log in order to get exact cause why it could not be started.
Here some usefull articles related to Apache issues:
- How to check that it is running on the server: http://kb.swsoft.com/en/1481