well that could be a couple things, but for one i'd say visit my guide:
http://flyforhero.ucoz.com/forum/25-1140-1 and there somewhere (search for it) you'll see a note made by eber on how to alter the neuz.ini in order to include the server IP and properly save it. thats probably whats causing the problem if you cannot log into your account.
if you cannot log into your character, server is down or lagged and keep trying