lost connection on primary comp from tm 2300 router

I have a westell wirespeed modem connected to a tm 2300 which in turn has a xps sec gen(primary) connected from the ethernet to the lan connection on the router and also have a wireless connection from the dell 4600(secondary)....the connectivity to the internet was perfect for the first week of operation for both desktops...then the xps dropped connectivity to the net but the wireless connection still works fine for the 4600...control utility on the xps can`t find a connection to the router.. .i`ve checked the firewall and security settings, even  bypassing the 2300 for a direct connection from the modem to the ethernet card on the xps ,the xps still doesn`t recognize connection..the ethernet card shows it has a link,diag on the card passed...all lights on both modem and router are  green and steady...i`ve reset both units,ran virus detection,it was clean and found no intrusions or hacks ...seems strange they would both work fine then the primary would drop out...i have`nt tried ping yet tho will do that when i get back home .....all suggestions appreciated...