I don't think so Karsten, I think it's definitely DNS issue because I had the same problem at work yesterday. After adding the site to my hosts file and clearing the cache on IE and FF they both still connected to the old server. I had to as our networkd admin to stop and restart our DNS services for them to update.
ping and tracert were both showing the new IP but apparently web browsers don't care much for the hosts file and just go to the DNS configured in your windows to resolve names.
I sent Jimmy a link to OpenDNS that shows how to change windows DNS', hopefully it's gonna fix his problem..........and if I were him I would move to a new ISP asap.