I had this error all day yesterday in Firefox, and in IE it was the usual unable to load page error. This was on a new install. My own blog had installed and worked perfectly, but this new install - into a different domain name on the root of the server - gave this error.
It turned out to be the htaccess file, because that was supposed to add the "www" part of my domain address (otherwise it comes out as http://mysite.com for example). For some reason, this stopped WordPress continuing the install. I renamed the htaccess file, and all was well. (Now I just have to worry about what happens when I un-name it again.)
Tricia