Have you done a Factory reset on it? (While it's on, gently but firmly press the end of an opened up paper clip into the Reset hole and hold the switch in there down 5-10 seconds until the lights on the router start to flash).
Sometimes a factory reset with some TG firmware can cause the wireless to be on by default without encryption and for the firewall to be off - it's always wise to go into the GUI and check/reconfigure the settings after a factory reset.
One can change that though by telneting the router and changing a few settings, not forgetting the saveall command of course. Might be worth while for the OP to telnet the router and check some of the settings since his wireless issue seems very odd?