Genymotion, "Unable to load VirtualBox engine." on Mavericks. VBox is setup correctly

Question

I keep getting the following error:

I have reinstalled, deleted and tried about EVERYTHING to get Genymotion to work again.

I do not have the device I need, but Genymotion was PERFECT for the job, until Mavericks update I have been fighting to get it to work again.

MacBook Pro, Retina 13-inch, Early 2013. i5, 8gb.

I'm running version 1.3.1 for os x. I do have Virtualbox 4.3 installed with Oracle_VM_VirtualBox_Extension_Pack-4.3.0-89960.vbox-extpack too.

My Virtualbox starts up normally without ANY errors. I tried Environment variables putting vbox on my $PATH, all sorts of things. Nothing works!

I have no idea what to do anymore, anyone out there had similar problems and fixed it ?

EDIT: LOG:

Oct 28 09:49:36 [Genymotion] [Warning] ****  STARTING GENYMOTION  **** 
Oct 28 09:49:36 [Genymotion] [Warning] Genymotion Version: Genymotion 1.3.1 
Oct 28 09:49:36 [Genymotion] [Debug] Network request to URL:  "/launchpad/last_version/mac/x64/" 
Oct 28 09:49:39 [Genymotion] [Debug] Genymotion server informs that version  "1.3.0"  is available from  "https://ssl-files.genymotion.com/genymotion/genymotion-1.3.0/genymotion-1.3.0.dmg" 
Oct 28 09:49:39 [Genymotion] [Debug] Version: "1" 
Oct 28 09:49:39 [Genymotion] [Error] Genymotion is newer than the database... how is possible? 
Oct 28 09:49:39 [Genymotion] [Debug] Getting currently authenticated user from  local cache 
Oct 28 09:49:39 [Genymotion] [Debug] Loading "vboxmanage" plugin 
Oct 28 09:49:39 [Genymotion] [Debug] Library loaded with success 
Oct 28 09:49:39 [Genymotion] [Debug] Chipset: "GenuineIntel" 
Oct 28 09:49:39 [Genymotion] [Debug] CPUID 0x1 (Intel): ECX= "7fbae3bf" 
Oct 28 09:49:39 [Genymotion] [Debug] VBoxManage path (default value): "VBoxManage" 
Oct 28 09:50:09 [Genymotion] [Debug] Can't run VBoxManage ("list", "hostonlyifs") 
Oct 28 09:50:09 [Genymotion] [Warning] QProcess: Destroyed while process is still running.
Oct 28 09:50:09 [Genymotion] [Error] "Fail to load vboxmanage plugin from /Applications/Genymotion.app/Contents/MacOS/plugins/" 
Oct 28 09:50:09 [Genymotion] [Error] Unable to find VM Engine. Plugin loading aborted. 

EDIT 2:

VBoxManage list hostonlyifs

Prints the following:

VBoxManage: error: Failed to create the VirtualBox object!
VBoxManage: error: Code NS_BASE_STREAM_WOULD_BLOCK (0x80470007) - Stream operation would block (extended info not available)
VBoxManage: error: Most likely, the VirtualBox COM server is not running or failed to start.

Answer 1

I had the same problem and solved it by running the following command:

sudo /Library/StartupItems/VirtualBox/VirtualBox restart

In later versions, the command is

sudo /Library/Application\ Support/VirtualBox/LaunchDaemons/VirtualBoxStartup.sh restart

Make sure you've unblocked VirtualBox's kernel extensions in System Preferences->Security and Privacy->General (You'll get a popup when you install VirtualBox).