Rusty, what's your resolution set to? I've tried it with IE 8 and I haven't seen any problems or seen any reports of this on the forum for this forum.
1280 x 800, 32 bit color
I generally don't have IE at that size though because I usually have it as a smaller 1/2 to 1/3 screen window.
All you have to do is fill up this message box with enough text that the scrollbar appears. Just grab some text from any window here and paste it in and then try to type text to the end of the box. As you type the window will bounce back and forth from the top to the bottom. The box vibrates back and forth between scrolled to the top and to the bottom. You can edit your text, but it's so difficult to see what's happening it's not worth it.
I don't remember if this was 100% reproducible, but I just opened IE to another website and tested this and the bug did not occur.
I really believe this to be an IE bug.