Well, I'm running IE 9 and 'Clearing Cache' has not fixed the endless right side box, however, by clicking the 'Toggle View' icon on the far right, it does 'close the box' for my reply post, except I do have to do it on every reply that I do (which isn't a big deal at all).
***Oops, I meant I have IE 9, not IE 7.
*Perhaps my problem is what I think is 'Clearing Cache' isn't what I think it is?? I'm not very good at computer technology lingo, so how does one actually 'Clear Cache'? I thought 'Delete Browsing History', which includes 'Clearing all your cookies', etc., was what is meant by 'clearing cache', but perhaps I'm misunderstanding?