Check if you’re referencing jquery.js BEFORE bootstrap.js and bootstrap.js is loaded only once. That fixed the same error for me:
<script type="text/javascript" src="https://stackoverflow.com/questions/9529574/js/jquery-1.8.0.js"></script>
<script type="text/javascript" src="https://stackoverflow.com/questions/9529574/js/bootstrap.min.js"></script>