Infrastructure cannot handle the load.
It seems the launch of Guild Wars 2 was even bigger than ArenaNet ever expected as they’ve had to temporarily suspend sales of Guild Wars 2 via the online store.
ArenaNet announced this unfortunate decision a few hours age on it’s Facebook page. The main reason for this decision is to ensure current players get the most enjoyable experience they can on the already extremely overcrowded servers; digital sales will be turned back as soon as the infrastructure is in place to handle the high load.
One thing to note: you’re still able to purchase the game via the retailer of your choice and play it as much as you want.
The recently launched MMORPG went through months of beta testing however the first week of the game being in the public’s hands has been filled with problems ranging from log in servers being completely inaccessible to major game crashes after attempting to create your character.