Microsoft live messenger freezes PC?

I have used msn for over a year with no problems but I recently did a complete re install on my pc, since then whenever I try to use msn with too in my IE browser at same time it always freezes computer, this has never been a problem before. I have tried uninstalling and reinstalling but itdoesn'tt make any diff. My pc runs vista and has all relevant updates. Any ideas why and how I can fix this, its really annoying. thanks