Should you find error messages in /etc/httpd/logs/error_log such as
[Tue Mar 28 04:29:42 2006] [notice] child pid 24546 exit signal File size limit exceeded (25)
This means that you have a log file that is great than 2GB in size. To fix this run
cd /etc/httpd/domlogs
du -sh * | grep [0-9]G

This should show you [...]