First of all reboot the STB, then reboot the router.
Can you get into the diag screen of the router? If so what does the IP address start with? If it starts with 10****** then the router just needs registering. Try going to
http://172.16.30.83 (I think) this should take you to the registration (start) page.
If the router IP starts with 169 or 00 you might have ethernet problems.
If the router IP starts with 80 or 82, your in business, cos it should be working.
Do not post your full IP on the forums if you reply.
Good luck.