I’ve been having this problem with many of my sites. The problem is intermittent and it happens in Firefox and IE and it happens on several different computers, PC and Mac. I have been searching the internet trying to find out why this is happening. I even tried switching hosting companies but that didn’t really fix it. Some of my sites never do it, but others have the server not found error and it lasts for several minutes or several refreshes before the site comes back up. I have domains purchased from several different domain providers. I’m not sure if it has something to do with the domains, hosting, browsers, internet security/firewall problems, or what. I hope this gets solved soon.