Do You have a D-Link wireless router and a cable modem ? It's important to get the terms correct so we don't get confused. What is the model and brand of the modem and what is the model of the D-Link router ?
To re-set the D-Link to factory specs you have to press the reset button and hold it for at least 10 seconds. The best way to press it in is to use a pen or something similar because the reset button can be very small and sometimes they are resessed in a bit.
Thank you, but I finally solved the problem by getting rind of the D-Link wireless router which was connected to an ADSL modem and purchasing a complete system which includes the modem with the wireless router. At least I now have a wireless system which works, but am a little poorer.