It was more than just fast pass, their entire computer system went down. At the ticket booths they had to manually process credit cards. At the entrance they stamped the date on tickets, pass holders had to show ID as they couldn't scan passes. You could pay for food and merchandise with a credit card, but when they slid it, all it was doing was storing the information for processing later, they were not able to authorize the dollar amounts like they normally would from what I was told, so hopefully they don't get too many cards that were maxed out. Also, I imagine the not scanning tickets is going to cause some issues for non ap guests with multi day tickets later on. Parking was free for most, if not all guests as they couldn't take card and it wouldn't be fair to give free parking to those who don't have cash and charge those that do. Basically anything that requires access to a server was down throughout the resort. Oddly though many nearby places were having problems with credit and debit cards, I don't know if it was related, but if you have used one in the area over the past couple of days, I would watch your balance.
By the time that we got there, they were down to one train, but that may been because of how close it was so close to park closing.