Apache log errors

[Dr-Host]

Hello,

I've taken a look at my /var/log/httpd/error_log

and I see alot of the following lines:

accept_mutex_on: Identifier removed
accept_mutex_on: Invalid argument

and one of those

[Sun Jun 25 16:23:49 2006] [alert] Child 4957 returned a Fatal error... \nApache is exiting!

what does the accept_mutex_on
mean and why after that, the apache went down?

Thanks.
David