if you aren't using DHCP (which should automatically set up /etc/resolv.conf for you) then you should have the following line in your resolv.conf:
nameserver <ip address of your ISPs DNS>
I have a feeling that if you are pointing to your router (which you aren't if you don't have 'nameserver' at the start of the line anyway) then it isn't going to work... because the router will not be running a DNS service (will it?)...
so you need to specify a valid nameserver that you know works.
(in windows XP, if it gets the DNS dynamically, I think typing 'ipconfig /a' or something will get you a table of data that includes the nameservers).
so then put them into the file as above.