My Wireless stoped working?

Got a Bigpond Tompson TG782T home gate way with 4 ports and wireless, my laptop is a asus brand new and iphone and my sisters older laptop and iphone arnt able 2 connect to the wireless. Ive tried going through and reseting the net work connections and stuff like that. I havnt changed any passwords, its a visible connection on my wireless options but it wont let me access it. if someone could help it would be much appreciated, oh and is it ok to restore modem back to factory settings?