Well it only came back up today. DNS servers can take up to 48 hours to update, depending on how they're maintained and such. They usually get working again after about 24 hours at maximum though.

You could also trying flushing your DNS cache:

Windows: IPCONFIG /flushdns
Mac (OS X): lookupd -flushcache
Linux (major distributions): /etc/rc.d/init.d/nscd restart

in your Command Prompt, console or terminal respectively.