I’ve had what sounds like the exact same problem the last several days. I tried from Chrome, FireFox, and IE and the “reorder” button is not working. The behavior in FireFox is slightly different in that pop up box for the quantity just spins when you click “Add to Cart”. In the other browsers, the pop up goes away but with all three browsers nothing ever gets added to the cart. Chatting with support has not been productive so far.
Craig