Bobubas said it doesn't make a difference.
Oh, welll...
But at least that puts the blame back on our "friends" at Microsoft.
One thing that's really frustrating, though, is that we can't even blame it on a particular version of IE. I checked the forum's access_log, and the people getting the really wide IM/posting window are using 4.01, 5.0 and 6.0, so there isn't even the possibility that upgrading might solve the problem.
But what's even more frustrating is that plenty of other people are using those versions of IE and they're not having any problems. :-
There must be something else that everyone with this problem has in common - but damned if I can find it...