Hi all this has become a real head scratcher for me. I have some users that are unable to access a particular website as themselves when in IE. If they are logged on, and I run IE as myself, they can access the site. If I log on, and run IE as them, they are not able to access the site. I have reset IE, cleaned temp files, reset registry and file permissions, no luck. So far the only fix has been to remove their windows profile, then build a new one. I did that for one user, it worked for a week or so, then the issue came back. The OS is windows 7 x64, on domain environment.
Try running that site in Compatibility View mode in IE. Its the icon to the right of the URL bar that looks like a broken page.