Milan: Thank you for your kind advice. It helped me a lot. Uninstalled as you kindly wrote and let your update service /etc/apt/sources.list: deb http://archive.ubuntu.com/ubuntu/ jaunty-proposed restricted - update the laptop. Though I don't know how to check the version, the bug is gone. Also the link is highly helpful (I overlooked it above, or read it days ago and forgot). It is thanks to people like you and those above that I can use this wonderful Ubuntu and learn, too. Thank you.
Milan: Thank you for your kind advice. It helped me a lot. Uninstalled as you kindly wrote and let your update service /etc/apt/ sources. list: deb http:// archive. ubuntu. com/ubuntu/ jaunty-proposed restricted - update the laptop. Though I don't know how to check the version, the bug is gone. Also the link is highly helpful (I overlooked it above, or read it days ago and forgot). It is thanks to people like you and those above that I can use this wonderful Ubuntu and learn, too. Thank you.