Trying to order tickets at www.renfe.es , but always get message: "Credit card operation not authorized'. Know all the info submitted is right! Any idea order not going through and how purchase can be made?

Try raileurope.com . They sell passes and point to point tickets for all of Europe.

Did you try contacting renfe customer service via the email on their website? I had issues with using my credit card and they promptly answered my questions and I was able to get it to work. Rail Europe is another option but you'll pay a surcharge.