Problem Resolving names into ip addresses

Hi,
I am a relative newbie when it comes to debian so please excuse any
assumption or lack of etiquette when posting. Anyway, here goes.

I have a box connected to an ADSL modem / DHCP server / NAT.

I upgraded to unstable version from a knoppix 4.0 base. This was to get
Xorg and to resolve some graphics card issues. One problem still
remains.
 
I am able resolve names (eg www.google.com) into their ip addresses using ping and nslookup but cannot with firefox and apt-get. Once I give the ip adress (like 200.0.0.3) to firefox and apt-get they work fine. I understand that bind is used and is somehow separate. Is there some config file (like in /etc/defaults) which I need to use?
 
I have used an apple computer on the same connection and it has no problems so I know the connection is good.
 
Any help would be appreciated.
ken.