Alliedassault - xbox live troubleshooting

Alright so i've been enjoying my xbox live latley, last night i took my xbox over to my friends house....hooked up my xbox on his big screen and we played halo 2 online for a few hours and had a pretty good time. Today when i tried to plug it back in at my house its saying "dns error" All of my cables are hooked up correctly.....(all i do is plug an ethernet cable from my xbox into my router) anyone else have this problem before? i looked on the troubleshooting page at xbox.com and they recomended unplugging the power and plugging it back in...which i did a million times and it hasnt worked yet....and i just got ghost recon 2 and men of valor from my cousin and want to play those online pretty bad cry: i havent played ghost recon 2 yet...but movv is pretty cool, even though i heard it sucked on pc. ANYWAYS, help please....anyone.....suggestions, tips, ANYTHING...