In your environment, you configure a Group Policy setting to prevent the tabs in Internet Explorer from closing. You expect that, when a tab is closed, a dialog box appears and the tab is prevented from closing. However, on a computer that has Internet Explorer 9 installed, the Group Policy setting does not work.
This problem occurs because Internet Explorer 9 introduces a new feature, known as fast tab shutdown, that hides a tab during shutdown. Unfortunately, the code that executes fast tab shutdown runs before the Group Policy Object settings are queried. Therefore, the tab in Internet Explorer 9 is hidden but is not successfully closed.
To resolve this problem, install this update.
Security update information
To resolve this issue, install the most recent cumulative security update for Internet Explorer. To do this, visit the following Microsoft website: