Amazon Kindle Books unavailable in the US - store offline?

It's no doubt just a temporary glitch, but it appears that no books are available in the Kindle store to customers in the USA, at the current time. I've noticed in the past that there are often database updates at noon pacific time (where Amazon's HQ is located) and that is the exact time that the Kindle store started blocking all US customers. I first noticed the problem with the free titles I posted earlier, but have checked some of their bestsellers, front page promotions and independent authors using DTP -- none of them are available to purchase.