When trying to reply to posts when you start to type a reply post longer than the window the cursor will scroll down out of view and you can not see what you are typing. You scroll up then start to type again and it scrolls down to the bottom.
This is a known Internet Explorer 8 hiccup.
The quick fix is:
click on tools
click on compatibility view settings
click display all websites in compatility view
click on close
It is fixed.