I saw this in a Windows mailing list and am curious because it seems so strange.
The writer was trying to help a neighbor using Verizon DSL with a D-Link DSL-2750B.
He was able to connect (wirelessly) to the router and ping and traceroute to sites such asand However, he could not get to any website with either Chrome or IE.
He was able to connect his smart phone to her network and could not get to any websites that way either.
He connected her laptop to his home WLAN and had no problems what-so-ever.
I looked up the manual for the router and in its default configuration, no ports are blocked.