Problem
Message "405.0 - Method Not Allowed" appears in the back-end (administration) area of Sitefinity 4.0 CTP, when trying to save/modify content items or configurations.
Cause
1. Sitefinity uses WCF RESTful web services. The essential part here is that the calls to the web services are done via HTTP protocol, and the web requests have different http verbs - put/get/delete - depending on the operation that should be done (storing new item/getting an item/deleting an item).
2. The WebDavModule is an extension of the standard http module, but WCF RESTful cannot work with it.
Solution
All verbs should be allowed in the web.config file. If this does not help, the WebDavModule should be removed:
<system.webServer>
<validation validateIntegratedModeConfiguration="false" />
<modules>
<remove name="WebDAVModule" />
Out of the box solution related to the WebDavModule will be provided in the later versions of Sitefinity.