If I understand your question, your OP endpoint is at a different path than server.aspx, and you've changed your XRDS file to reflect this, but RPs are still attempting to connect at server.aspx. Is that right?
...assuming it is...
Your OP typically doesn't cache this, but RPs often cache discover results for some period of time. It may just be that RPs haven't noticed the change yet. You can try some OP tests at http://test-id.org, as any RP-side cache there has been disabled, to see if you got it right.
Another possibility is that your OP has two XRDS documents -- one for user identity URLs and one for your OP identifier. Make sure you change both of them with your new OP endpoint.