Have you tried changing browsers? Opera Fire Fox, or something, just to check its not a browser setting?

If you can get in with one browser and not another, its a browser setting, if it doesn't matter what browser, then its either IP, website setting, or could be something with your exceptions in your security settings for windows. For that last one, make sure you have windows SP2 for XP installed, and then check any internet blocking software you have. Norton is pretty bad about this particular feature.

ID