In the fullscreen editor, if I paste copy and paste text, upon paste, the editor scrolls to the top of the post every time. I am on Mac OS X 10.7.3. I am on Safari 5.1.5 (7534.55.3).
Chrome 18.0.1025.162 has the same problem.
I can reproduce the problem consistently. It is not intermittent.
In the regular (not fullscreen) editor, I have no problem.