Hello, I don't think this is a browser version issue as it happened to me with IE6 and IE8. I used fiddler to debug the problem and its because IE hangs when it hits a 404 error (Note - only under certain mysterious configurations - probably connected to the add-ons or toolbars being used - search google for more details). The 404 error is my case was for soundcontroller.swf. The fix to protoutil.js mentioned here worked for me. I also had to add an extra sound-config.xml to my root directory but that might not be the case for everyone.
Anyway, once i fixed all the 404 errors, the chat room now works fine in all versions of IE.