If you get the following error, or errors:
[Wed Nov 16 08:37:07 2011] [emerg] (13)Permission denied: couldn't grab the accept mutex
[Wed Nov 16 08:37:08 2011] [alert] Child 5376 returned a Fatal error... Apache is exiting!
[Wed Nov 16 08:37:08 2011] [emerg] (43)Identifier removed: couldn't grab the accept mutex
[Wed Nov 16 08:37:09 2011] [emerg] (22)Invalid argument: couldn't release the accept mutex
[Wed Nov 16 08:37:11 2011] [emerg] (22)Invalid argument: couldn't grab the accept mutex
AcceptMutex flock
to your main httpd.conf.Other reports claim that doesn't work, and that the following does, so see which works best for you:
AcceptMutex posixsem
Note that when adding customizations to the main httpd.conf, you'll need to use one of the two methods to prevent your settings from being lost.
Reference: http://blather.michaelwlucas.com/archives/678