I just finished installing CentOS 5.6 on my machine and when i tried to start httpd service I encountered this error
"httpd dead but subsys locked"
Googling around I foudn this commands
check for running processes
ipcs -s | grep apache (more info @ http://linux.about.com/library/cmd/blcmdl8_ipcs.htm)
stop processes
ipcs -s | grep apache | perl -e 'while (<STDIN>) { @a=split(/\s+/); print `ipcrm sem $a[1]`}'
Remove httpd lock file
cd /var/lock/subsys
rm httpd
restart httpd and check status
Taken from http://blog.linuxvin.com/?p=150