Here's an Ubuntu 14.04 Vagrantfile

This should fix vbguest issues in bug-1001567 as well.
I ran into a namespace collision using 'ubuntu/trusty64' as a box name with Vagrant. I happened to have an image for another system lying around with that name. I ran 'vagrant up', whereupon Vagrant happily booted up the VM that was configured for another project, and DXR exploded all over the place.

Prefixing the box version with 'dxr' or something else that is project specific makes those namespace collisions unlikely.