Cannot purchase Gems!
I am not sure, but you can always submit a ticket to Customer Support, and they will assist you.
support.guildwars2.com
This has happened to me as well.
I recently got back from a deployment and forgotten my password, i had to get customer support to reset my password so i can use it on my new laptop.
Before i had password help, i was able to purchase gems just fine, afterwords im unable to finalize payments, i think the customer support has flagged my account as unsafe or something.
In case of moderators assistance:
Reference 130427-000705
I have been having the same issue. I’ve tried several different cards, but none of them seem to work. Hopefully arena net will fix this issue soon.
ArenaNet Communications Manager
Guys, I believe these should be in the Black Lion Trading Company forum, so that folks working with the Gem Store can help you. Feel free to post there, but more importantly, you should know that we cannot help you through a forum post. We can help if you submit a ticket, so please contact Support and the team will help you. You can read through the Knowledge Base on that link, and you can submit a ticket via the “Ask a Question” tab on that page.
For details on what information you should provide in your ticket, to expedite its response, please read The “How to Submit a Ticket” post.
Communications Manager
Guild & Fansite Relations; In-Game Events
ArenaNet