Checkout problems - coupon code?

[Guest]

I cannot successfully check out from my site. I have had problems with the checkout just looping you through over and over making youi sign in again and again. I think I got that working, but now I get some weird coupon error. The table it is looking for is there. I am lost and have wasted the whole day. can someone go through my checkout process and see what is up?

 

http://www.carterartworks.com

 

thanks!