Simply unbelieveable! One of our IP address is/was being pointed to a PORN site. When I brought to the attention of our webhost, they said I would have to contact the registrar of the the domain and ask they why my IP as being directed to their site. They also said it would be a big deal, because the domain expired in couple of days. SO I sent a email and I've never heard back.
Well, now Google has indexed the site under the PORN name and now when you click on a link, you get a DNS error.
It Sounds like your hosting company does not know how to run A DNS Server. It's is all on their back, not the registrar. Someone screwed up the "A records". You should have an "A record" for www and the domain name itself.
Have them update the "Start of Aurthority" Record's Serial Number to 2003050315(today's date with 15" and The "Time to Live Record" to a shorter period than 1 day(maybe 1-3 hours) then tommorrow change it back to 1 day. Then they should do a manual "Update of Server's Data File".
I would change hosts to someone like Dell Host or Use a DNS service like Versign, if they don's fess up.
This is assuming your DNS records are pointed to the hosting companies "Name Servers".