Check if in IIS settings for the site you have enabled the option for AnonymousAuthentcation and all other authentication optiosn are disabled. This depends on the authentication your site is using, by default the authentication is Claims Authentication (the authentication type can be checked in Administration->Settings->User Authentication), here is the documentation for the IIS setup:
Perform one of the following:
- If you are using Forms authentication, make sure Anonymous Authentication and Forms Authentication are enabled and all other authentications are disabled.
- If you are using Claims-based authentication, make sure only Anonymous Authentication is enabled and all other authentications are disabled.
If you are running sitefintiy on IIS 6 follow the steps in our guide, you should not be experiencing any problems, as we have tested Sitefinity with such settings and is working as expected. In addition to our instructions can you verify that you have configured IIS as described in the blog post as well:
Can you make sure that all handler mappings are correctly set as per the above blog post, as we have encountered similar issues in the past with other users, who did not set the mappings for the services correctly.
The following article can also be useful:
the Telerik team
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