just keep trying. it took me a fair few attempts but i eventually got through. just keep clicking the account link and have your password in the clipboard so you can paste into the pw box and be really quick at typing in ur username. Even after getting to the pw form it usually bombed me out but just kept hammering at it until it lost patience and let me in
I had some problems with subscription page and I found out that these things can help to get it working:
1. Use Internet Explorer, when I used Opera to pay it just gave me the try again in three hours.
2. Turn off proxy server (or make an exception for billing.camelot-europe.com).
3. Empty cache and cookies.
4. Refresh the page.