I have an OpenID relying party setup and using XRDS. It passes the \"RP has discoverable return_to\" interop test over at http://test-id.org/RP/DiscoverableReturnTo.aspx.
After 3 hours of work i had satisfied AOL verification. Below is what you need to make sure(assuming you satisfy openid 2.0 specificaiton).
Aol is making http Head request, so make sure that your realm page is accepting Http Head request. I think that's what mostly wrong as we don't check Http Head ever.
Aol http head request is very naked so make sure your serve back response with bare request. ie. in our case code was also failing when there is no agent info in request.
It is most likely you would have problem with above conditions.