Page Not Found error after registering a new user

Hi,

I've just installed beta 5, but now when I try to register a new user, I get a "Page not found" after typing in the facebook user credentials.

The browser address bar shows the following: http://example.com/fbconnect/register/import

If I then try to access a different page, I keep getting redirected to the above URL with the same "Page not found" message.

Could you tell me what have I done wrong, please?

Thanks!