Are the thumbnail controls missing or not being displayed in your Windows 7 taskbar? An update is available that enables the thumbnail controls of certain applications, and makes them display correctly on the taskbar in Windows 7 or in Windows Server 2008 R2.
This update addresses an issue in which the thumbnail controls for some applications are not displayed on the taskbar.
After you install this update, you may have to restart your computer.
Download links: KB2259539.