Some ie6 bug prevent from properly clearing the options of a select html element. This is an issue the actual length that myselect.options.length statement returns. The smart way to do this is with a while loop.

            function removeSelects(elementId){
                var myselect = document.getElementById(elementId);
                for(var i=0; i<myselect.options.length; i++){
                    myselect.options[i] = null;
                }
                while (myselect.options.length > 0) {
                    myselect.options[0] = null;
                }
            }