Well connecting the Linksys and then connecting the Netgear to that seems to work, so shows its not a faulty router

(good diagnostic test i guess)
Though it
could be a faulty WAN port on the router??
I say the above because when you plug the netgear into the linksys you would have (i presume) used one of the LAN side ports?
Can you access the router once you plug it into the modem (ie on it 192.xx.xx.xx address?)
You can manually release and renew (on most routers) your WAN IP address. Make sure that the WAN IP of the router is set to be given by the network (DHCP).
What we know:
Its not a faulty modem - because Linksys on its own works OK!
LAN Side of Netgear = OK (though WAN side may be iffy)
Cables are OK.