I created a simple page using the code provided by this page (the first sample):
http://www.dotnetopenauth.net/developers/code-snippets/programmatic-openid-relying-party/
But I can’t seem to get it to work, I can redirect to the provider but when the provider redirects back to my page, I get error 500, “The request was rejected by the HTTP filter”.
I already checked ISAPI filters which I have none.
I discovered that I’m using Isa in the server, so I just followed this instructions to get it working.
http://blog.brianfarnhill.com/2009/02/19/sharepoint-gets-the-error-the-request-was-rejected-by-the-http-filter/