Un-Fuck the VirtualBox

If you are like me who tried to configure ssh working from  Host OS to Guest OS by doing the steps from this Blog and got this   "Configuration error: Failed to get the "MAC" value. 
VBox status code: -2103 (VERR_CFGM_VALUE_NOT_FOUND). " error while starting the machine,Here is how to fix that annoying error.
Just open a terminal window and do
You have to replace the <Machine name> with your Virtual Machine,and use escape the spaces with a backslash like "Ubuntu\ 10.10"

$ VBoxManage getextradata <Machine name> enumerate

This will display the keys that you have configured for your machine,you will have to unset the keys that you have added.
You can do this simply providing an empty value for the key.


Im just pasting my output to make things clear for a newbie.

aji@mbp:~$ VBoxManage getextradata Ubuntu\ 11.04 enumerate
Key: GUI/LastCloseAction, Value: shutdown
Key: GUI/LastGuestSizeHint, Value: 640,480
Key: GUI/LastNormalWindowPosition, Value: 480,141,640,342,max
Key: GUI/LastScaleWindowPosition, Value: 550,118,640,480
Key: GUI/MiniToolBarAlignment, Value: top
Key: GUI/SaveMountedAtRuntime, Value: yes
Key: GUI/ShowMiniToolBar, Value: yes
Key: VBoxInternal/Devices/pcnet/0/LUN#0/Config/ssh/GuestPort, Value: 22
Key: VBoxInternal/Devices/pcnet/0/LUN#0/Config/ssh/HostPort, Value: 2222
Key: VBoxInternal/Devices/pcnet/0/LUN#0/Config/ssh/Protocol, Value: TCP

I have added the last 3 keys manually,so lets just go ahead and remove the custom keys by executing the following 3 commands.

aji@mbp:~$ VBoxManage setextradata Ubuntu\ 11.04  VBoxInternal/Devices/pcnet/0/LUN#0/Config/ssh/GuestPort
aji@mbp:~$ VBoxManage setextradata Ubuntu\ 11.04 VBoxInternal/Devices/pcnet/0/LUN#0/Config/ssh/HostPort
aji@mbp:~$ VBoxManage setextradata Ubuntu\ 11.04 VBoxInternal/Devices/pcnet/0/LUN#0/Config/ssh/Protocol

And we're done.Now start your VirtualBox,it will run without any problems.
Hope this helps someone.