Oracle recently announced the VirtualBox 4.3.20, a maintenance release of VirtualBox 4.3 which improves stability and fixes regressions.
For Linux, the new release fixed the Linux Kernel 3.18 compile issue and some full screen mode issues on X11 hosts. For the detailed changes, please see the official changelog page.
How to Install / Upgrade to VBox 4.3.20:
Method 1: Grab the .deb installer.
Depends on your OS type, 32-bit (i386) or 64-bit (amd64), download the .deb installer from the official link below:
Virtualbox For Linux Download Page
For Ubuntu 14.10, select download the package for Ubuntu 14.04. Once downloaded, select open the package via Ubuntu Software Center and click the install button.
Method 2: Add Virtualbox repository and receive future updates:
Oracle provides an official Virtualbox repository for Ubuntu Linux, so far Ubuntu 10.04, Ubuntu 12.04, Ubuntu 12.10, Ubuntu 13.04, Ubuntu 13.10, and Ubuntu 14.04 are supported.
To add the Virtualbox repository, press Ctrl+Alt+T on keyboard to open terminal, and then run the command below:
sudo sh -c 'echo "deb http://download.virtualbox.org/virtualbox/debian $(lsb_release -cs) contrib" >> /etc/apt/sources.list.d/virtualbox.list'
For Linux Mint, replace $(lsb_release -cs) in the code with the code name of the based Ubuntu release, such as trusty, precise, raring, etc.
Then download & import the keyring:
wget -q https://www.virtualbox.org/download/oracle_vbox.asc -O- | sudo apt-key add -
Finally, you can install the package virtualbox-4.3
via your package manager, or by running the commands below:
sudo apt-get update sudo apt-get install virtualbox-4.3
For future 4.3.x releases, just run regular system updates via Software Updater will bring you to the latest.
After updating to Kernel version 3.18, VirtualBox kernel modules got messed up. Thanks to your crisp steps, Vitualbox is all fixed and works like a charm :)