Unable to start Genymotion Virtual Device - Virtualbox Host Only Ethernet Adapter Failed to start

This worked for me using GenyMotion 2.0.3 and VirtualBox 4.3.6. My problem was I have an existing host-only adaptor that is used by Vagrant. I can't simply delete it, it will trash my Vagrant VM.

Create a new host-only adaptor in the Virtual Box global settings.
Give it a separate address space from any existing host-only adaptors. For example, I set mine up as follows, where I also have a vboxnet0 (used by Vagrant) that uses 192.168.56.x

name: vboxnet1
IPV4 address: 192.168.57.1
mask: 255.255.255.0

DHCP:
address 192.168.57.100mask: 255.255.255.0low bounds: 192.168.57.101high bound: 192.168.57.254

Then, edit your existing GenyMotion VM to use this host-only adaptor, and restart it from GenyMotion.

Good luck!

I have a same problem and I solve it with this :

1. Open Windows Network Connections
2. Right click on VirtualBox Host only adapter that created
3. Choose properties
4. Check "VirtualBox NDIS6 Bridged Networking driver"
5. disable and Enable the adapter

I had the same issue and this fixed it:

Go to Network and Sharing Center > Change adapter settings and enable these:

• Local Area Connection (if it's disabled)
• VirtualBox Host-Only Network

I think that enabling the second will do the job, but I did the first anyways.

Hope it helps.