This update addresses an issue experienced by some users where CPU usage is high when they are navigating a page that contains multiple frames or when multiple frames are navigated simultaneously. This occurs when the phishing filter evaluates the page for each navigation, resulting in multiple simultaneous evaluations for the same page.
If you have experienced any such performance issues, you are encouraged to download and install this update.
This update is now available on Windows Update for Windows Vista users and will be made available in February for Windows XP and Windows Server 2003 users. All users can download it now here along with related KB article 928089.