I had a quick look last night, and it seems to me that their nameservers are down. Personally I would be surprised if a nameserver got hacked, because usually it's the only role for a particular machine, so all that needs to be done is for the OS to be reasonably locked down and patched, the DNS service too and perhaps an SMTP service too for reporting.
Plus, if the nameserver got hacked, then why not stick an additional "fingers up" at the site administrators by changing the DNS for the website to point at a "we hacked you" type page - I'm sure there's one on the Internet somewhere so the hackers don't give away any information that might identify them. It's what I would expect from a standard prank hack job.
