Well ... thanks for the reply, but that's is not my problem.
I cannot access any website with telnet or a browser if I don't use IP instead of hostnames. Adding all those hosts to my hosts file is obviously not an option.
Programs other than nslookup or ping cannot resolves hostnames from the dns server it seems.
If I try the following command: telnet www.linuxquestions.org
it says that it tries to connect to 18.104.22.168 which means that it resolves www.linuxquestion.org
as ip address 22.214.171.124 which is very unlikely.