I went through the same thing 3 months ago. I had 2 prepaid Amex gift cards that I had received as gifts and were both valued at $100 and they were at first denied by Amex when I went to charge the full amount towards my final payment. I called the cc and they said there is an automatic 20% held back on any restaurants, hotels or travel an that it would take 3-7 days to get that hold released. So I ended up charging $80 on each card which left me a balance of $20. Well the balance did not get released till after 30 days which was ridiculous. I ended up using it later for gas. Moral of my story - don't use prepaid cards even if they were received as gifts for anything travel or restaurant related. At least mine was a small figure, good luck..