Sending multiple VBoxManage commands can cause VBox GUI to hang

[rdghickman]

We have scripts that issue multiple VBoxManage commands to start/stop VMs. Very often if multiple commands are sent and you interact with the UI (mostly with the VM that VBoxManage is acting upon) the GUI will freeze/hang indefinitely and often VBoxManage will as well. Terminating the GUI forcibly and restarting it makes it fine until you again single left-click on the VM in the UI upon which time it freezes again. Rebooting Windows makes VBox usable again but leaves the VMs in state aborted.

Staggering VBoxManage commands seems to be a workaround with at least partial success.