This week the IE Blog posted an entry about an update to IE 7 to rectify a performance issue with the IE 7 Phishing filter:
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.
I haven’t experienced the problem, but if you have you should download and install this update which is available on Windows Update for Windows Vista users and will be made available in February for Windows XP and Windows Server 2003 users. IF you can’t wait for patch Tuesday, when I assume it’ll be released for XP and Server 2003, you can download it now going to the KB article 928089.