webperfcache has got port 80

I am trying to deploy to Mac OS X Server 10.3.7. A "Listen 80" instruction 
in httpd.conf produces an error when apache starts up, complaining that the 
port is already in use.
lsof -i tcp:80
tells me that a process called webperfcache has its grubby hands on port 80.
If I disable webperfcache in /etc/hostconfig apache works ok. Can anyone 
advise on how important webperfcache is if at all for dynamic WO apps and 
why I am getting this clash?
Thanks
John