My scenario was that a windows update installed IE9 but I was required to work on IE8. So I uninstalled IE9 and I was back on IE8. Everything was working fine before this uninstall. But suddenly after uninstall, IE8 started taking too much time to load web application, even refreshing the page was going to stuck every time and it was consuming 100% CPU.
What I did was I tried this option.
Go to Tools, Internet Options, Advanced and Click Reset. you may select the "Delete personal settings" check box as I did, and then click on reset. It will take some time and ask you to restart the IE8. After that everything works fine...:)
You may try another option of disabling the Ad-On services by doing this
Go to Tools, Options, Programs, Manage Add-Ons.