Virtual Box - Critical Error - Failed to create the VirtualBoxClient COM object

I was running a VM when it fell into an error state because of lack of disk space. I killed the process with kill <pid>, as it wasn't responding, closed VirtualBox, and freed up some space on my partition. After rebooting the computer, I proceeded to start VirtualBox again, and was presented with this pop-up.

Failed to create the VirtualBoxClient COM object.

The application will now terminate.

Document is empty.

Location: '/home/adminvb/.config/VirtualBox/VirtualBox.xml', line 1 (0), column 1.

/build/virtualbox-gBjstP/virtualbox-5.0.40-dfsg/src/VBox/Main/src-server/VirtualBoxImpl.cpp[534] (nsresult VirtualBox::init()).

Result Code: NS_ERROR_FAILURE (0x80004005)

Component: VirtualBoxWrap

Interface: IVirtualBox {0169423f-46b4-cde9-91af-1e9d5b6cd945}

I can't even start VirtualBox's menu. I'm looking for a way to fix it that hopefully doesn't require me to reinstall everything, as I wouldn't like to loose all my virtual machines. (I will do it if it's absolutely necessary.)

I'm running VirtualBox on Linux Mint 18.1 64-bit.