DR Danise - With the way the board is now set up, if you use the "back" button to get back to a page, and then try to respond to another post on the same page, the board's software will assume that you are "accidentally" re-posting the same response. The quickest fix is just to click on another Page number, and then click on the Page number you were posting to originally.
As for your Quick Reply box, it sounds like you might have "collapsed" the Quick Reply box. Just click on "Quick Reply" (which is to the left of Reply Box) to open it back up.