Das Werkstatt

[PROBLEM]
I've tried to "import" an already existing Virtualbox VM-client to a new setup:

1. Copy the VM-client folder as-is from old setup to the folder where your VBox VM-clients reside.
2. Add the machine: "Machine > Add"
3. Then selected the ".vbox" file.

Worked like a charm, but since that machine was left in a "Saved" state (on its original Virtualbox setup), I got an error message like this:

Nonexistent host networking interface [...]
VERR_INTERNAL_ERROR

[SOLUTION]
Open the "Settings" for the newly added/imported machine and set the network adapter(s) to "Not attached".
Then resume the machine, power it down correctly - and then reconnect the network adapters as usual