Core problem is this JavaScript function. When the timer runs out, the value is set to ' ' instead of ''.

    function freezeFrame(elementid) {
        if(document.getElementById(elementid) !== null) {
            var answer=document.getElementById(elementid);
            if(answer.value == '') {
                answer.value=' ';
            }
            answer.blur();
            answer.onfocus=function() { answer.blur();};
        }
    };

So, this would be easy to fix, but are there possible side effects? The test for answer.value =='' was added in revision 7699 by c_schmitz.

Fixed in revision 12335

1.92RC4 released