I would suggest you ask to be passed to a senior technician. I've tried to look at your web site hosting and the code and it appears as if the last part of the code wasn't transfered to my PC. That could be to do with Apache or MySQL.
DNS wise, have a look at
DNS Stuff: DNS tools, DNS hosting tests, WHOIS, traceroute, ping, and other network and domain name tools.. There are a few things but support should be able to sort them for you.