Zywall 100 USG - unable to connect user/s to SSL VPN

I've followed the guides to setup a SSL VPN, created users, created groups, added users to groups, set the address, downloaded secuextender, its' the correct version.
log files show user connecting, and then disconnecting straight away. I've changed passwords, deleted users, re-added, still unable to secure a connection.
Secu extender client replies with disconnection. Definately entering in the correct passwords.