It appears that several players have successfully purchased the digital copy of StarCraft II, Grafix. I, personally, am unable to determine what would be causing your transaction to fail; however, our Billing department may be able to shed a little more light on this for you. I encourage you to give them a call using one of the following numbers:
Billing and Account Services
Live Representatives are available every day from 7:00 AM to 8:00 PM PDT For phone assistance please call: 1 (800) 592-5499 || 1 (800) 59-BLIZZARD
Players in Australia should call 1-800-041-378
Players in Singapore should call 800-2549-9273
Players in Chile should call 1230-020-5554
Players in Mexico should call 001-888-578-7628
Players in Argentina should call 0800-333-0778
All other international players should call: (949) 955-0283