what I've found (several times) is that if there is a clash with w: not existing (which sometimes happens), an error in httpd.conf or rotatelogs not being correct (or already running in memory) the server will start so you get the front page, but then immediately shuts down again. Normally a reboot would clear it, but i've since found out that having a valid httpd.conf, or killing off rotatelogs in memory would allow me to restart the server and get it working again.