A strange problem for your consideration - I've recently signed up to telecom (spark) VDSL service and received a new HG630b router. I've run a LAN cable from the PC in front room to the router, but no network connection is registered. I can hook my laptop up with the same cable and everything works ok. I then hooked PC with the same cable to the old router, and then to new router with a new cable and everything works!
It's just the direct PC to HG630B router LAN connection is the issue.
I've had a look in the router settings in each but I cannot see anything different. I've contacted Telecom support and they said bring the PC to a repair guy, and weren't much help. I think it's just a setting in the HG630b that needs fixing.
Any help is greatly appreciated