OWA 2003 Page Can Not Be Displayed

I have three remote users who are unable to get onto OWA 2003 for their email. Other are able to, but for some reason these three cannot. They are all at the same location, but even another user at that location was able to access the website. They are using the same laptop models that other who are able to access OWA as well. I have gone over their IE 6 configuration settings and they are the same as mine (I have the same model laptop and am able to access OWA). I do recall there are locations where I seem to be unable to access it. In addition to a network connection for all of them not working, they each have a modem card and using that they are still unable to access OWA. Any ideas on what to check next?