add: document.getElementById("menu-numberofweeks-inview").removeAttribute("disabled"); 
context: CalendarWindow.prototype.switchToMultiweekView = function calWin_switchToMultiweekView( ){    document.getElementById("month_view_command").removeAttribute("checked");    document.getElementById("week_view_command").removeAttribute("checked");    document.getElementById("day_view_command").removeAttribute("checked");    document.getElementById("multiweek_view_command").setAttribute("checked", true);    this.switchToView('multiweek-view');}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/3854ba67435f93e2bc52231c2cb37f05afc3e2bc/calendarWindow.js/buggy/calendar/resources/content/calendarWindow.js