New VirtualBox 3.1.4
How to update VBox Guest(Ubuntu) Additions?
1. use Vbox install option in GUI to download file "VBoxGuestAdditions_3.1.4.iso". The file was put into "C:\Documents and Settings\Administrator\.VirtualBox", and hint to mount. It will be mount to "/media/cdrom"
2. go to this directory and run
sudo ./VBoxLinuxAdditions-x86.run
Before do this, you might want to run
sudo apt-get install build-essential linux-headers-generic
3. restart guest OS (virtual linux)
Note: If you already download a *.iso file, you can mount it manually in vbox media manager.
P.S.: vbox 3.1.4 still has an annoying problem "could not switch the monitor configuration... CRTC56"!