I have one form in a PHP (5.2.9-1) application that causes IIS (Microsoft-IIS/6.0) to throw the following error when POSTed:
The page you are looking
The acceptable verbs are controlled in web.config (found in the root of the website) in and possibly . Web.config will be accessible to you if it exists. There is also a global server.config which probably won't. If you can get a look at either of these you may get a clue.
The acceptable verbs can differ with the content types - have you set Content-type headers in your page at all ? (i.e. if your Content-type was application/json then different verbs would be allowed)