My problem started this morning.

I have a couple of discount codes I want to use (1 from ebay, 1 from FlyBuys). But when I go to checkout, there is no space to enter the code. I have logged in using FireFox and I have logged in using Google Chrome - the problem appears on both browsers.

I thought maybe it's because I was trying to pay for items I had already been invoiced for, but when I added a 'new' item to my cart and went straight to checkout I still had the problem.