If you use Hotmail accompanied by Outlook Express 6 and you recently updated to Internet Explorer 7, you may encounter a problem where upon opening Outlook Express you receive an unknown error with the details stating that it could not connect to the HTTP server for Hotmail.
I searched and found that this is due to IE7 and that there is a fix.
You need to download the patch that matches your operating system be it Windows XP, Windows XP 64-bit, Windows 2003, etc.
I downloaded and installed the patch and it fixed the problem. Hope this helps.