the problem is that your router is old.
your router only supports ipv4 and backtrack is enabled by default to ipv6.
how to solve the problem?
1) open firefox and type on the url part 192.168.1.1 or 10.0.0.1
you'll enter to the routers configuration. And now if possible change the settings (press Advanced settings if aviable) from ipv4 to ipv6.
2) just buy a new router. they are cheap and you can get one from ebay for less then $ 15 with ipv6 enabled
I hope this was helpful
if you have any more questions, just aks