This can't be a true bug, since you're the only one experiencing it. Some basic ideas: If you see the same problem on the mojoPortal demo site, it's an issue with your browser or browser settings. Check security settings and try another browser if possible. If it works on demo but not your site, it could be skin-related. Try a different skin on your site and see if that helps.
Also see the Basic Troubleshooting document.