I had an issue of Web Sites NOT rendering in IE9 for a site that I have running locally in IIS. I could, however, render the page in IE9 on another machine and it worked just fine. My issue was just locally and ONLY when I used the local machine name. i.e. http://localhost WORKED! But http://MachineName DID NOT work. So to fix my issue I just addedhttp://MachineName to the Local Intranet Site list in IE9.
Tools -> Internet Options -> Security -> Local Intranet -> Sites. Then Addhttp://MachineName to the list. Uncheck the https checkbox if just adding http.
Then it all started working locally. I'm not sure why this is as I have other servers that work just fine. I have never come across this issue until now. Good news is that it works now, but I would like someone to explain why I had to do that in the first place.
BTW, this was on a Windows 2008 R2 after installing SQL Server 2012 Reporting Services and SharePoint 2010 Enterprise.
Hope this helps someone!