Xbox live DNS error no matter what I do.

[noxlumos]

Hi, I've got a DNS error repeatedly coming up on my Xbox live. I've checked the Ip, Dns addies etc and all seem to be correct, or am I being monumentally stupid in some way ( quite probable)?
Connecting to broadband via a Belkin wireless router, but all items are hardwired at the moment.
Any suggestions would be greatly recieved. thanks in advance

[Mattk]

how are you connecting manual or auto ?

[noxlumos]

I'm with Orange broadband and they say everything has to be set to auto. So it finds the IP like that then comes up with DNS error, DNS servers could not be found. So I rang them again and they gave me a two manual configurations and they didn't work either, so they are suggesting it's a Belkin issue, swearing it should all work on auto anyway. Belkin are like talking to aliens who've taken a don't care pill, so now I'm stuck. Thanks.