Deborah,
it might not be just the quotes, or may be not the quotes at all, but anyway on first inspection, that is something I noticed that could possibly cause the behavior you reported.
If this requires changing the footer file in the theme, please clear the QuizPort cache before retrying the quiz. (Site admin -> Modules -> Activties -> QuizPort -> Clear cache)
BTW, I was able to log on as that student, but I could not see how to quickly get to the quiz without changing post-conditions, and I didn't want to do that on your live site. As a result, I haven't actually been able to try that quiz as that student and reproduce that behavior. It's safer if you do the testing I think.
If you do get the error again, please view the source of the page that is in your browser when you get the error, select and copy the entire source code, save it to a text file, and send it across to me in a private email.
Hopefully though, you won't get the error
regards
Gordon