I haven't read through all this thread, so apologies if this has been reported already.
I'm using IE8 on Windows Vista at the moment. On entering my text into the box when making a post, I find that, if I exceed the size of the window (cue scroll bar) the window will keep on scrolling up. As I type, the cursor remains in the same place, and I get a brief image of what I'm typing before it scrolls up again. This means I have to scroll down manually to check what I've written. The moment I type it scrolls up again.
I didn't have that problem with Firefox. Unfortunately that browser is playing up in other ways (not related to this site, by the way, it just gets verrrrrry sloooooow, on occasion) hence my reason for using IE.