jqmodal not scrollable on a Mac with latest Firefox?

Question

Any idea why a new Firefox (latest version) would not show scrollbars on a JQModal? Worked fine in every other browser:

Called like:

    $('#HTMLPreview').click(function(){

        var a=document.getElementById("txtStudentWriting").value;
        b=a.replace(/[\r\n]/g, "<p><p><p>");

        $.modal(b,{maxWidth:500,maxHeight:600,minHeight:500,closeHTML:'<a     href="#">Close</a>'});

        return false;
    });

include: <`script type="text/javascript" src="../include/js/jquery.simplemodal-1.3.5.min.js">