If the login/register pages are just refreshing when you attempt to submit data it is possible that you've been linked to a phishing page.
I'm on the silkroad just now and everything's working fine for me.
Here is the correct link to the silkroad, make sure that the one you're visiting is the same.
http://silkroadvb5piz3r.onion/If you have the noscript plugin you might want to try enabling javascript for the silkroad, but be warned that could endanger your anonymity if the site was compromised, but unless you're buying things you don't really need to worry about that
(If enabling javascript works I'd recommend disabling it once you've created your account)