I have been trying to book Prado tickets for my family for 15 May 2009. For the last two days I keep getting a "communication error" message. When I try to call the listed user assistance number I keep getting a busy signal. Any ideas?

Just curious why you need to book tickets in advance? Do advance tickets get you a special entry?

If I remember correctly, an advance ticket allows you to enter via a different entrance than the "masses". So, you don't need to stand in line if you have an advance ticket.

Oh... come to think of it, that was exactly what I did last year. You can read about the entrances here:
http://www.fodors.com/community/euro...omment-1545461

For the OP, could it be a problem with your credit card blocking the charges?

BTW, at which point during booking did you run into difficulty? I just tried a dummy booking and I was able to select your date and a list of times. I didn't go on further when it asks for my name/address etc.

The error message occurs after you confirm that you want to proceed to what I believe would be the payment screen. No problem selecting date, times, and entering name/address.

No issue with credit card since I never get to a page to enter that information. I have tried with three different browsers - IE, Firefox, and Google.

I see what you're saying now. I am getting the same error message. How about trying the other phone Tel. +34 91 330 2800? Good luck.