So I found this error when viweing my intra application with IE7. No error with Mozilla Firefox.
After some debugging, I know the error come out from the onmousemove event. It is not specifically from this event alone, actually it is from a database content which is passed to this event. One of my user type in a special character, and when the string is passed to onmousemove event, it trigger an error such as the string is incomplete.