MS has released an update for IE7 that will rectify the issue of your machine slowing to a crawl on some occasions when the anti-phishing tools are at work.
The feature that protects against fraudulent Web sites, new in IE 7, in some cases could bog down computers running Windows, according to an article on Microsoft's support site published Tuesday. This could happen when a Web page contains many frames or when a user browses many frames in a short time, the company said.