403 Forbidden

Whenever I first connect to the internet with Internet Explorer, the first page that loads always goes to

This happens wheather it is the home page or any other page.
The status bar will breifly display: cache.freeserve.net before I get the message, despite my not using freeserve for my ISP.
The problem developed a couple of months ago, and only on two of five userspaces on my computer.
I've just updated to Internet Explorer 7 and completely reset to default settings, but this doesn't fix it.
Can anyone help me sort this out?
This happens wheather it is the home page or any other page.
The status bar will breifly display: cache.freeserve.net before I get the message, despite my not using freeserve for my ISP.
The problem developed a couple of months ago, and only on two of five userspaces on my computer.
I've just updated to Internet Explorer 7 and completely reset to default settings, but this doesn't fix it.
Can anyone help me sort this out?