cannot access server

Okay, I'm stumped

I am trying to access a webserver from a PC and the browser tells me the server is down. Tried pinging it and I get a timed out response. nslookup fails to find the server. tried turning the firewall off, tried checking the content setting in the internet options, tried explorer and firefox. all with no luck. The user can email people at the site without any problems. The workstation can access pretty much any other server

I know the server I am trying to access is up and running because if I go down the street to another computer, I can browse the site and ping the address with no problems. Not only that, the site has around 500 subscribers and no-one else hase any problems.

There is something weird going on here. Any thoughts would be good. I am running Spybot on the workstation at the moment but have no real hope that it will turn up anything.

Workstation is a pentium 4 running Windows XP from a small office using a Seimens Speedstream modem.