Today I upgraded my Vagrant and VirtualBox to the latest version (1.8.1 & 5.0.12-104815) and did the vagrant up.
I got this from Vagrant:
==> default: Waiting for machine to boot. This may take a few minutes...
The guest machine entered an invalid state while waiting for it
to boot. Valid states are 'starting, running'. The machine is in the
'poweroff' state. Please verify everything is configured
properly and try again.
If the provider you're using has a GUI that comes with it,
it is often helpful to open that and watch the machine, since the
GUI often has more helpful error messages than Vagrant can retrieve.
For example, if you're using VirtualBox, run `vagrant up` while the
VirtualBox GUI is open.
The primary issue for this error is that the provider you're using
is not properly configured. This is very rarely a Vagrant issue.

When I tried to start this box from VirtualBox I got this error message:
'HostInterfaceNetworking-VirtualBox Host-Only Ethernet Adapter #2' (VERR_INTNET_FLT_IF_NOT_FOUND).

Solution was to remove VirtualBox and install it again with the following parameter:
-msiparams NETWORKTYPE=NDIS5

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