I have a similar issue with PayPal. Can't charge PayPal for over 2 weeks now though I've used it successfully on other sites this past weekend. Assumed the Nexon problem would be fixed when the rankings/site was fixed.
But I am still getting this:

when all i have done is clicked the paypal button here:
I'm not "misentering" anything, I never even get the chance. Just one click and denied. Yes, I logged a ticket but now I'm frustrated that others are able to charge PayPal yet I cannot on any acct from any of the 4 computers I've tried. Seems like it's not Nexon's site and is something directly related to my acct. Makes no sense.