Try the following.
Go to the command prompt and type "nslookup". It will try to connect to the
DNS servers in sequence. If it tries one server and gives a time out and
then connect to any other successfully, then move it up the DNS servers list.
If all the DNS servers are timing out you may have to contact your ISP and
get the propper DNS server IP address and add it to the DNS servers list or
get the router configuration updated in case you are obtaining a dynamic IP
from the router.