So sorry to hear that your application was returned - a lot of people are having trouble with their credit card. Please do not be disheartened. If Canada is your dream, please do reapply, especially if you've collated some of your documents already. There's only 1000 in each NOC for post 26 June applicants but they only changed the rules recently so there should be spaces available if you send in your application soon. I don't know if a bankers draft is safer than cc - can they refuse that?
It's so sad that so many of the May applicants are being rejected. At over $1,000 dollars Canadian for the application fee, you would think they could at least call you or e-mail you if they hit a snag such as a box not filled in or the credit card rejected. It's very upsetting. But I guess the staff are just following the rules in the op 6 guidance. Good luck to you.