When I try to connect to Xbox live, I always get a DNS failure aftter the IP adress has been confirmed.

Things to know:
I brought my xbox to my friends house the other night
I tried power cycling it
I have a router and a wireless network adapter (2.4 GhZ)
Ive been playing live for about 2 years now
I am using comcast as my Internet service provider and lynksys as my router and adapterr
They are both set to automatic (the IP adress,Gateway,DNS, etc...)

PLEASE HELP ME, I'M BEGGING YOU

Should I buy a new adapter?