That could be part of his problem. I would start with his modem though and a ping/traceroute. If he can not resolve the name that would indicate something is wrong with his DNS. Then the next step would be to see if he can do a traceroute by IP.
If he has a cell phone he could also ping on his address from some outside server and see where it is breaking down but that does not always work with all ISPs (I know it works with TW).