>I don't think anybody is using my user name and password. But your suggestion to check the browser setting is what I was looking for, as possible cause of the problem. I will check it and also will check if ZoneAlarm is not the culprit.

Simply put it off for a while and see how it goes. This one and several others have caused problems to UT and several other sites as per their builtin behavior. We talk a little bit about that in our Technical Guidelines.