cannot start client in virtualbox after reinstal of binaries

[Humphrey van Polanen Petel]

attempt to share folders in virtualbox results in the error "adduser: The group `vboxsf' does not exist."
a suggestion found on virtualbox.org was to reinstall the binaries
X86 virtualization solution - base binaries were removed and installed
upon starting a guest, virtualbox manager gives error "Kernel driver not installed (rc=-1908)"
see attached

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: virtualbox-qt 4.3.10-dfsg-1ubuntu5
ProcVersionSignature: Ubuntu 3.16.0-50.67~14.04.1-generic 3.16.7-ckt16
Uname: Linux 3.16.0-50-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.15
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Oct 8 21:01:04 2015
ExecutablePath: /usr/lib/virtualbox/VirtualBox
InstallationDate: Installed on 2015-09-08 (30 days ago)
InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
SourcePackage: virtualbox
UpgradeStatus: No upgrade log present (probably fresh install)

[Gianfranco Costamagna (costamagnagianfranco)]

Can you please try virtualbox from my ppa?
https://launchpad.net/~costamagnagianfranco/+archive/ubuntu/locutusofborg-ppa/

[Humphrey van Polanen Petel (hpvpp)]

After restarting the host (Ubuntu on Dell Vostro 420), Virtualbox is working fine.
FYI this is what I remember doing
--
install Virtualbox from Ubuntu Software Centre
install Windows XP
windows screen doesn't fill available window
couldn't access usb
couldn't share directories
run $sudo adduser humphrey vboxuser
usb now accessible
run $sudo adduser humphrey vboxuser
fails with "group vboxsf does not exist"
tick "guest additions" in "X86 virtualization solution - base binaries" in Ubuntu Software Centre & click <apply changes>
no effect
remove & reinstall "X86 virtualization solution - base binaries"
virtualbox reports error "Kernel driver not installed (rc=-1908)"
--
I decide to explore first before reinstalling virtualbox from the ppa at launchpad
--
I find references to "insert guest additions CD image"
I find the entry on the "devices" menu of virtualbox & execute it
I can share directories
--
I don't remember at what points or how often I rebooted the virtual machine, virtualbox and/or the host
I hope this helps

[Humphrey van Polanen Petel (hpvpp)]

Is this problem fixed now?

[Gianfranco Costamagna (costamagnagianfranco)]

Lets close

[Humphrey van Polanen Petel (hpvpp)]

OK

Good idea to clean up.