So let’s say you are using IE9 and you go to the Site Navigation Settings page on a 2007 SharePoint site and see this:
Try this. Start IE9 without any add-ons by executing
Then, navigate to the same page and voilà, your navigation editing area appears!
This must be due to some malcontent add-on.
Enabling and disabling add-ons and refreshing your page brings you to NameCtrl Class being the add-on that seems to be causing the problem. Disabling this add-on fixes the issue…at least it did for me!
NameCtrl Class Microsoft Corporation
Add-on issues with IE9 and SharePoint 2007 navigation