This question already has an answer here:
I am continuously attempting to install VirtualBox on Ubuntu 14.04, but I continue to receive errors.
Kernel driver not installed (rc=-1908)
The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or there is a permission problem with /dev/vboxdrv. Please reinstall the kernel module by executing
as root. If it is available in your distribution, you should install the DKMS package first. This package keeps track of Linux kernel changes and recompiles the vboxdrv kernel module if necessary.
After receiving this error, the Ubuntu sidebar and desktop disappear. I am able to resolve this issue by reinstall the desktop and unity. However, I am told elsewhere to purge and remove everything VirtualBox related and then reinstall. I have attempted to reinstall both through Ubuntu's Software Center, but have also gone the path of installing the .deb file from VirtualBox's website.
I have browsed through both Ubuntu and VirtualBox forums without success. Any help is much appreciated.