Clients cant surf.

I am the administrator of a small network using cisco routers. I have four routers connected to a central router that is connected to a WAN. Each router is running two eathernets. None of the users on my network can reach any site on the www but users that are conected to the same WAN that are not going through me are able to surf. When my clients run a traceroute they get through my network, through the wan and into the www before they time our somewhere around 16-18 hops. Everything was fine until yesterday when this started happening and I have made no changes to my routers. The WAN administrator assures me he has no blocks in place.
HELP!!!!!