Here is a <a href=”http://www.tech-faq.com/public-dns-servers.shtml”>List</a> of public DNS servers. Try using one of those instead of the DNS you have now. Also check the uptime status of your router and any managed switches or WAP’s that your are using. It could be that these are resetting for some reason. You might also try replacing the NIC or updating the driver for it in your computer.
Check the cabling to your computer. Check with your IT support staff about the LAN switch port setting for your connection. Ask them to check the DHCP configuration on your computer and on the server. What is the lease time setting for DHCP addresses? There could also be some malicious traffic flooding the network blocking your computer.
What services patch is on that computer.
Some easy things to check are, open a command prompt from the run tab.
In the dos windows type in ipconfig /all and see what DNS servers are listed.
Now in the same dos window ( providing that there are DNS servers listed ) then ping and address such as www.msn.com you are not concerned with response only with name to ipaddress resolution. If you get the resolution than it is not a DNS problem.