I've recently started using VirtualBox and find it really good. However, I was setting up port forwarding with NAT according to the documentation and must have made a mistake since I got the following error while restarting the virtual machine
Failed to start virtual machine XYZ -56 (VERR_NO_DIGITS)I tried to remove the newly added settings using
vboxmanage setextradata XYZ ... <null>but I guess I had a typo somewhere in my initial attempt to use setextradata, and I couldn't figure out what the typo was (I had closed the command prompt window and there was no history available). I couldn't find anything online using google so I simple deleted the virtual machine and added it again using the same vdi...worked like a charm. Hope this helps someone out there.
I had the same problem but I did not have to delete the VB. If you edit (Windows Vista path) C:\Users\<account>\.VirtualBox\Machines\<virtual box name>\<virtual box name>.xml you will see all the port forward details saved. You could remove the XML line causing the error. In my case it was obvious...
Nice one, I was looking for this and i got it.