Apache & MediaWiki

I've been getting this annoying error message on my MediaWiki page whenever I enter special characters or word "perl".

Method Not Implemented

MediaWiki was installed on test machine so I didn't even bother to fix it until now. The error was due to the software firewall mod installed on Apache. I've temporally disabled firewall only from my workstation computer IP by entering following line to /etc/httpd/conf.d/mod_security.mod:

SecRule REMOTE_ADDR "^192\.168\.14\.1$" nolog,phase:1,allow

Update:Found more problem with mod_security with some other web application so I ended up disabling the apache mod. The server is not on the web, only serving local network, so shouldn't be any security threat though.