Please Help!

Hi.
I have a WordPress site which has been working lovelily until I upgraded my Internet Explorer to I think Internet Explorer 9 or something. Now, I copy text to add a post into the ‘add new post’ function online, but when I go to adjust the html, it doesn’t open! I’ve been getting similar issues in switching from html to view modes and keeping formatting after switching or even saving my post! Any ideas or even a tip on where to get info?

Thanks!