Here is the error that occurs with instant checkout when using the 5 step checkout process. I've cleared cookies and this does not fix the problem.
This webpage has a redirect loop
The webpage at http://www.xtracomfort.com/order?step=2 has resulted in too many redirects. Clearing your cookies for this site or allowing third-party cookies may fix the problem. If not, it is possibly a server configuration issue and not a problem with your computer.