I'm not the best Network guy out there, but I know enough to tell you this:

First, since connection to a web site, or other server, isn't a direct one, you have to go through many other serves routing the information (hops). Each of these hops slows your connection down a little, and if one of them is slow, it'll slow the whole transfer.

Usually, the information will try to pass elsewhere when it can't reach using the fastest way (that's when you get "Timed Out" with pings) but if it doesn't get timed out, but is still slow, most of the time it's going to continu the same path. If it does Time out, it may try to go elsewhere, but probably still going to try the first path most of the time.

If your using Windows, your friend here is the command "tracert". Use it as you use "ping". It'll tell you where it's slow between you and your target. It kind of s*cks, but there's little you can do against that.

One thing you can try, is to disconnect your modem (yes, even if you have high speed), and reconnect against after 30 seconds or so. It MAY, at that point, try another route to reach the target. It's not 100% garanteed, but that's probably your best shot.

Next best thing to do, which also s*cks, is to quit and wait for it to get better.