VirtualBox 4.3.26 on OSX 10.10.2 Fails to install

I am trying to install VirtualBox on my iMac and it keeps failing right at the end of the installation process. The end of the log file shows

Mar 23 07:59:22 AlexsMac installd[61695]: PackageKit: Using trashcan path /var/folders/zz/zyxvpxvq6csfxvn_n0000000000000/T/PKInstallSandboxTrash/49EB706E-4F98-4A99-B7CB-D1EEB9834CFD.sandboxTrash for sandbox /var/folders/zz/zyxvpxvq6csfxvn_n0000000000000/C/PKInstallSandboxManager/49EB706E-4F98-4A99-B7CB-D1EEB9834CFD.activeSandbox
Mar 23 07:59:22 AlexsMac installd[61695]: PackageKit: Shoving /var/folders/zz/zyxvpxvq6csfxvn_n0000000000000/C/PKInstallSandboxManager/49EB706E-4F98-4A99-B7CB-D1EEB9834CFD.activeSandbox/Root (3 items) to /
Mar 23 07:59:22 AlexsMac installd[61695]: PackageKit: Executing script "./postflight" in /private/tmp/PKInstallSandbox.kc88cc/Scripts/org.virtualbox.pkg.vboxkexts.vhtUfg
Mar 23 07:59:23 AlexsMac installd[61695]: ./postflight: (kernel) Can't unload kext org.virtualbox.kext.VBoxUSB; classes have instances:
Mar 23 07:59:23 AlexsMac installd[61695]: ./postflight: (kernel)     Kext org.virtualbox.kext.VBoxUSB class org_virtualbox_VBoxUSB has 1 instance.
Mar 23 07:59:23 AlexsMac installd[61695]: ./postflight: Failed to unload org.virtualbox.kext.VBoxUSB - (libkern/kext) kext is in use or retained (cannot unload).
Mar 23 07:59:23 AlexsMac installd[61695]: ./postflight: (kernel) Can't remove kext org.virtualbox.kext.VBoxDrv; services failed to terminate - 0xdc008018.
Mar 23 07:59:23 AlexsMac installd[61695]: ./postflight: Failed to unload org.virtualbox.kext.VBoxDrv - (libkern/kext) kext is in use or retained (cannot unload).
Mar 23 07:59:24 AlexsMac installd[61695]: ./postflight: /Library/Application Support/VirtualBox/VBoxDrv.kext failed to load - (libkern/kext) different version/uuid already loaded; check the system/kernel logs for errors or try kextutil(8).
Mar 23 07:59:24 AlexsMac install_monitor[62885]: Re-included: /Applications, /Developer, /Library, /System, /bin, /private, /sbin, /usr
Mar 23 07:59:24 AlexsMac installd[61695]: PackageKit: releasing backupd
Mar 23 07:59:24 AlexsMac installd[61695]: PackageKit: allow user idle system sleep
Mar 23 07:59:24 AlexsMac installd[61695]: PackageKit: Install Failed: Error Domain=PKInstallErrorDomain Code=112 "An error occurred while running scripts from the package “VirtualBox.pkg”." UserInfo=0x7f90d0471f40 {NSFilePath=./postflight, NSURL=file://localhost/Volumes/VirtualBox/VirtualBox.pkg#VBoxKEXTs.pkg, PKInstallPackageIdentifier=org.virtualbox.pkg.vboxkexts, NSLocalizedDescription=An error occurred while running scripts from the package “VirtualBox.pkg”.} {
    NSFilePath = "./postflight";
    NSLocalizedDescription = "An error occurred while running scripts from the package \U201cVirtualBox.pkg\U201d.";
    NSURL = "file://localhost/Volumes/VirtualBox/VirtualBox.pkg#VBoxKEXTs.pkg";
    PKInstallPackageIdentifier = "org.virtualbox.pkg.vboxkexts";
}
Mar 23 07:59:24 AlexsMac installd[61695]: PackageKit: Running idle tasks
Mar 23 07:59:24 AlexsMac Installer[62850]: install:didFailWithError:Error Domain=PKInstallErrorDomain Code=112 "An error occurred while running scripts from the package “VirtualBox.pkg”." UserInfo=0x7fee1bfeb5b0 {NSFilePath=./postflight, NSURL=file://localhost/Volumes/VirtualBox/VirtualBox.pkg#VBoxKEXTs.pkg, PKInstallPackageIdentifier=org.virtualbox.pkg.vboxkexts, NSLocalizedDescription=An error occurred while running scripts from the package “VirtualBox.pkg”.}
Mar 23 07:59:24 AlexsMac installd[61695]: PackageKit: Removing client PKInstallDaemonClient pid=62850, uid=501 (/System/Library/CoreServices/http://ift.tt/1qyOSZZ)
Mar 23 07:59:24 AlexsMac installd[61695]: PackageKit: Done with sandbox removals
Mar 23 07:59:25 AlexsMac Installer[62850]: Install failed: The Installer encountered an error that caused the installation to fail. Contact the software manufacturer for assistance.
Mar 23 07:59:25 AlexsMac Installer[62850]: IFDInstallController 1BD7B280 state = 8
Mar 23 07:59:25 AlexsMac Installer[62850]: Displaying 'Install Failed' UI.
Mar 23 07:59:25 AlexsMac Installer[62850]: 'Install Failed' UI displayed message:'The Installer encountered an error that caused the installation to fail. Contact the software manufacturer for assistance.'.

I have tried the installation several times after using the Uninstall tool included in the package but it keeps failing each time.

Tried Googling for an answer but don't seem to fin anything on this topic. Tried several different search terms.

Can anyone help please