Ok, time for a challenge!
I have had 2 PCs over the weekend that have come up with the same issue (other 10 clients and 4 servers working a treat).
We have a DC which is also running as our DNS and DHCP server.
2 machines over this weekend wouldnt get an IP address from the DHCP server. I have checked that the DHCP server has available leases and removed any old records that are not used any more. I checked that other machines would release and renew their IPs (firstly removing the entry in the DHCP server), this works fine. I changed the cable on both machines to no joy. The machines are connected to working hubs that I have other machines on - have used other ports on the hub to make sure this is ok.
As a result, i tried giving the machines static IP addresses and static DNS entries. The machines can ping anything via IP address, even address on the internet all ok. BUT they will not ping by name. I have double checked the settings, compaired to other machines etc. All other machines on network are resolving fine.
At this point i started to shooting in the dark.... checked my host file for rouge entries, ran hijackthis for random stuff, ran a full virus scan with 4 day old definitions, downloaded the latest drives from intel, i even installed a NEW network card and ended up with the same problem. Then as a last resort i ran the windows repair with no joy.
I am pretty sure this is just a client problem and my DNS and DHCP server are working fine.