To check your dns configuration and response, use this site :
http://www.checkdns.net/quickcheck.aspx
They give you a fast up to date situation. DNS starts resolving after 10 minutes to 24 hours, depending on the update frequency of the main dns servers ...
Also, clear your cache, otherwhise you could still see a non responsive site, even if it is ...
This is why to use the tool above.