sorry i say something you did already but here goes
you cant normaly use the usb and network points at the same time on the cable modem
so you most likely need to set the modem back up first ( or computer rather ) to use it on a network card rather than usb
( you might be able to miss that stage out )
then swith everything off plug cable modem into the router plug the computer into the router and switch on
realy the computer should see the change and set itself up ( though i often have to remind ie explorer where to look )
then you should be able to access the belkin router via
http://192.168.2.1/
and set up the wireless network options from there
if it isnt that simple i would be thinking its broken or has wrong cables ect