If you install VDS it automatically installs VDI agent.
from cmd run
You should see an entry like this :
Code:
2XVDSAgent.exe 3364 2X VDI Agent.
In your farm ( if you removed VDS try re-installing it )
Click the enable check under the farm -> VDI Hosts section near your local machine.
Click apply.
If it was disabled try enablilng --> apply disable --> apply to cycle the scripts.
See if this helps you.
I have the setup here and vbox does not appear to behave like yours.
Anyway I am running 3.0.8 64 bit your version has not been tested yet.
Vbox scripting is quite dynamic and they change quite some behaviors across versions.
Go for a supported version.
Hope this helps.