wiki forbidden message on specific words

I have a weird situation regarding this wiki: http://www.dvartora.com/Wiki/en/index.php?title=TestPage

This wiki is version 1.16.0

If I add the word "free"(so it will write: "Avast! Free Antivirus"(without quotes)) between the 2 words and try to save it says I am forbidden.

Forbidden

You don't have permission to access /Wiki/en/index.php on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

You can try it for yourself to see the result.

During installation I had a problem, th开发者_如何学编程at I bypassed doing a local install and uploading to the server, that it said I am forbidden(the same error).

I added the word "free" successfully. However, "Free Antivirus" does not work but "Free stuff" does.

Looking at the version they have no unusual extensions added.

So it seems likely that Treffynnon is correct - but I can't find the functionality. =:-(