IE 8 freezes after an upgrade from IE6

Dear All,
I got a problem with my Internet Explorer. I recently did an upgrade from Internet Explorer version 6 to version 8. What I have noticed is that my Internet Browsing slowed down a bit. It seemed that it is not on its usual self. I even encountered that after opening three tabs, it will froze down. I do not want to change browser as I am really comfortable using Internet Explorer 8 and I also liked the way I can open with many tabs, but thinking about this situation makes me feel that I made a wrong decision to upgrade it. By the way, I am using Windows Vista machine if it may pose a conflict with IE8.
