Since the homepage loads normally but other pages don't it tells me the DNS lookup on your ISP's primary DNS server has the site in its cache. Therefore, there is no point in trying another DNS server, or even your own ISP's secondary DNS server.
Since both browsers, IE and FF are giving the same result it doesn't appear to be a browser configuration issue either. Although it's theoretically possible both could be experiencing the same setup problem.
Given the fact you said this is the only site that is slow (?), and only pages other than the homepage, it's somewhat baffling, but not unsolvable.
Unfortunately, in order to do so it might require some further investigation into other settings on your PC besides those of the browser/s themselves.
Am I correct so far in describing the issue?
ps: I think of a computer the way a carpenter thinks of a hammer. That is, they are merely tools that allow me to perform certain operations. Simply put, I'm not a computer guru. However, tenacity and patience often helps in these types of situations and those are traits I rely on much of the time.

So, let me ponder this for a bit and I'll think of something, even if it turns out to be a large hammer.
