Try selecting Spanish as the language and see if it will accept your "State" input then. I believe that's what I've seen others indicate has worked for them (it's a known issue with the website).
Also, have you tried using the IVR to refill? Call 611 from your cell phone and you will be given an option to "add money" - you can use a credit/debit card, a check, or an at&t refill card with a PIN number to do a refill in this manner.
=^..^= There must be a happy medium somewhere between being totally informed and blissfully unaware.