I cant even order from green man gaming. Its declining my card for absolutely no reason. Most frustrating website ever.
For what it's worth, this happened to me, also. A quick call to my bank (on the number listed on the back of my credit card) and a quick run through an automated process let me buy from GMG. I think if you don't travel much whatever algorithms they've got in place to detect fraud kick in when you order from a site in a non-U.S. country (GMG is based in England).
Like I said, this was easily resolved, but is sort of a pain. Worse, it locked up my credit card from further use until I'd resolved the issue by calling and having the hold cleared.