DNS Error

[Fetal_Infection]

I'm getting an DNS error on both my xbox an my computer. I have cable internet and I have an ethernet cable coming from my cable modem to a port in my cable/dsl 4 port linksys router. Then I have I have ethernet cables from my two computers and my xbox into the other ports on the router. The original computer that had the calbe set up works fine through router, but on the computer that didn't get set up I just plugged the ethernet calbe into the back. I had DSL at my old house and it worked fine through this way but after I moved and got a new ISP it doesn't work anymore.

EDIT:When I try to just hook the computer or xbox up directly to the cable modem is says connected then unconnected connected then unconnected ect ect