Kam, i think i submitted this before, what it's doing (if i remember right). When you tick the box for my previous address or w.e it is, it then complains you haven't filled in the hidden address fields. SO if you untick the box put the address in manually it works.
(it might be the box saying same as billing address cant remember)
hope this helps
Piercy
I had to type in both a new delivery address and a new billing address. Hopefully it has saved them and next time it'll work