DC DNS Errors blocks internet traffic

[Maudy]

I am getting 4005 and 4015 error on my Windows 2003 DC. Because of this all of my internet gets blocked for domains on the controller. I can still notice that we have internet as our voice system is setup on a separate server and my router can ping some outside websites. I even noticed that my network still have some outgoing traffic. Still I am unable to detect the actual cause to the problem. Can you help me out?

[Lemog]

Do you have ISA on your Windows 2003 DC? Do you also have DHCP or DNS server configured on the same server? How much memory does it contain, did you tried to upgrade the memory? Another thing, try to ping google or yahoo and see if you receive any response from the sites. This should tell you about the connection strength.

[Maudy]

We don't have ISA. We are having Linksys firewall. Yes my domain controller also serves as DHCP and DNS server. I test my connection by changing the DNS address and it helps for say 30 sec but then the same problem reoccurs. I will definitely try to increase the memory as you said. However I couldn't ping google from command prompt which although works from my router.

[Lemog]

Is it possible to restart your DNS/DHCP server? If yes then do that. Have you tried to visit any website using the IP address? I think you must be knowing how did you setup your server, and so how you configured your primary and alternate DNS server's? Getting 30 secs of internet doesn't indicate anything because that's the default timeout interval on Windows computer.

[Maudy]

Restarting the server didn't had any impact on the problem. It is still the same. I think that's because each computer in the network have static IP. I have also tried to visit the site using the IP address but that too didn't worked. I am planning to stop the DNS server and see what happens to the network. Actually I had upgraded my Windows Server from 2000 to 2003 and since then I have some or the other problems arising.

[Amie]

Did you checked to which DNS server your Windows 2003 server is pointing to? Also try to do run "nslookup" from a computer when the internet is down. BTW please clarify me if I am wrong: you have a single domain controller with only one network card in your LAN. The DNS server points to this server for all DNS related tasks. But in such case how is external domain names are being handled?