A peculiar browsing problem

If you have no advice on this one, I won't be disappointed or surprised. Other people have been trying to solve the problem for months without coming up with an effective solution.

I've been using a particular Website for my job for years, but at the end of October some of the pages on the site, which just happened to be the most useful pages, suddenly became inaccessible to me. The page starts to load, then stops, and I get an error message, telling me the page is unavailable at this time. There are about 200 users of the site and only 7 of us have been affected in this way. We appear to have nothing in common beyond this problem. I have an AT&T DSL connection, five of the others have Comcast connections, and one has some obscure DSL connection, so obscure that I've forgotten the name of it.

After fiddling with the Website to no avail, the administrators advised us to try dialup connections. They work, and all of the pages are now accessible, but it is extremely irritating to pay for high-speed DSL and then have to plod along at 45 Kbps whenever I have to access this site, which can be dozens of times each day.

Here's something that might provide another clue. On the same day (October 30th) that those pages became inaccessible, I started getting an error message every day when I turn on the computer and go to my home page (Yahoo mail). It tells me that the operation has been aborted because Internet Explorer cannot open the Yahoo mail page. It's an absolute lie, because the home page is fully visible behind the error message box, so I simply click the "x" on the box and proceed as usual.

Any ideas? I've tried asking AT&T, but every time I type out the big long explanation, the site tells me the message can't be sent because they're having "temporary technical difficulties." I suspect those are not that "temporary," as I've never been able to send them an error message yet.