I had the same problem and couldn't figure it out for almost a day. I added IUSR and NetworkService to the folder permissions, I made sure it was running as NetworkService. I tried impersonation and even running as administrator (DO NOT DO THIS). Then someone recommended that I try running the page from inside the Windows 2008 R2 server and it pointed me to the Handler Mappings, which were all disabled.
I got it to work with this:
Now try refreshing your website.