I had the same problem, I am by no means an expert with linux I am a begginer, but I fixed the problem after looking all over the server for the conf file that should list my DNS listings, I found one of the hosts file was missing the DNS entry, so I used VI to edit the file and added the DNS entry, Specifically UNDERNEATH the 127.0.0.1 if you change or remove this it is very bad. Each time I reboot I have to make the entry again, I believe the file is hosts.conf under the etc dir, good luck.
Dave