Might want to check if there are any errors in syslog or messages.
The apache error log might not get written to if:
no space left on device (but there is space): http://carlosrivero.com/fix-apache---no-space-left-on-device-couldnt-create-accept-lock
In case that link dies before my blog does, here is the jist:
check logs for something like this: apache2 crit (28)No space left on device: mod_rewrite: could not create rewrite_log_lock check for left over semaphore files: ipcs -s If apache is not running and you see some running as the apache user, you can kill them off with this: ipcs -s | grep www-data | sudo perl -alne 'qx(ipcrm -s $F)'
That last bit assumes the user www-data. I stole that from the comments section of the line blog linked above. Thanks anonymous poster to another blog out there! You saved me a
bit of time. Thanks to Carlos Rivero as well for the initial find on this issue.