I simply must disagree that it is the credit card company's fault.
1) My credit card works perfectly well with every other European travel website.
2) I called and they said they had no record of any attempted purchase from Renfe.
3) The web is full of complaints from people who are having maddening difficulty buying tickets online with a credit card from Renfe specifically.

Every once in a great while a transaction will go through, and that is with a U.S. credit card. But I must say that if you are watching costs, and want to take into account the ridiculous amount of time you'll waste buying Renfe tickets on line, you might want to consider taking a bus instead. It's cheaper, and the websites work just fine.

mmmmm..or could it be user error?

I too use an American credit card and as well as it working perfectly on other European travel sites it also has worked perfectly on Renfe.

I've bought discounted tickets twice online with not a single problem and last week cancelled, online, tickets purchased for later in the year. The funds are already back in my credit card account.

As has been said many times:

1) use Maribel's guide for buying Renfe tickets and make sure you use the correct web address which is listed there. The link on her page takes you to the Renfe page that offers discounted tickets (in 4 languages including English). The English link on the Renfe homepage takes you to a bookings page that does not offer those discounts.

http://maribelsguides.com/mg_renfetickets.pdf

2) read the superb article on Trip Advisor and follow the instructions there:

http://www.tripadvisor.com/Travel-g1...s.Online..html