Forms

We have a number of quizzes set up in one form, the delegate selects the quiz they want and completes the questions, normally once they have completed a quiz and submitted their answers, they can select the Back button, select a different quiz and Submit that.  I had 3 delegates open up todays quiz but one of them could not display the selection question as the navigation Back button and the Submit button were missing.

Any ideas as to what could cause this and if there are settings that could be changed to make the form function on that PC?