I have the same browser and setup on my machine and it works fine.
The RTE features of a browser are built in and don't need to be enabled.
Try changing your security settings to a lower level and see if that helps. It could also be a plugin installed on your version of IE or pop up add blocking software that is coursing the problem.
If you still can't get it to work, then you will need to disable the use of the RTE in your forum settings, or change to a better, faster. less buggy browser like Mozilla Firebird http://www.mozilla.org/products/firefox/
I starting to find that most web developers and computer people are changing over to this browser for it's better performance, fetaures, and the web developer tools, like javascript debugging tool.