在VBox中安装完系统后，点击Device --》Install Guest Additions...
弹出错误对话框，提示下面：
Could not find the VirtualBox Guest Additions CD image file /usr/share/virtualbox/VBoxGuestAdditions.iso or /usr/lib/virtualbox/additions/VBoxGuestAdditions.iso.
Do you wish to download this CD image from the Internet?

然后，点击【Yes】，从网上下，结果又提示：
Failed to download the VirtualBox Guest Additions CD image from http://dlc.sun.com.edgesuite.net/virtua ... Ubuntu.iso.
Error downloading http://dlc.sun.com.edgesuite.net/virtua ... Ubuntu.iso - server replied: Not Found

如果vbox是新立得或者软件中心安装的，需要同时安装：virtualbox-guest-additions-iso
原贴见http://forum.ubuntu.org.cn/viewtopic.php?f=65&t=354549