D2 Lockbox can be a real PITA to install but it surely is even more PITA when it is installed in a VM. Thing is that even if you have a properly installed D2 Lockbox it will stop functioning after each VM reboot.
It took me long hours to notice what is wrong, I was changing the setup, double checking it with the documentation a few times and everything seemed just fine…Funny enough after changing the setup I was doing a reboot – “just in case” 🙂
So, the lesson I have learnt is that  VirtualBox VM should not be restarted after Lockbox was configured. It is better to use “VM Pause” otherwise D2.lockbox file will have to be re-generated.