The guys at Canvas in the US are looking into this, I contacted them on 27th December to inform them that there have been problems, and have received the following from my contact there:
I have been informed by Miami that some of the servers hosting the reg pages have been recieving intermittent service.
They are looking into this.
Apologies for the inconvenience.
So I would suggest you keep checking the site, and with a little luck the registration page will be back up and running later today.