Bringing machine 'default' up with 'virtualbox' provider...
==> default: Box '1404-64bit-virtualbox' could not be found. Attempting to find and install...
default: Box Provider: virtualbox
default: Box Version: >= 0
==> default: Box file was not detected as metadata. Adding it directly...
==> default: Adding box '1404-64bit-virtualbox' (v0) for provider: virtualbox
default: Downloading: http://hmn-uploads.s3.amazonaws.com/salty-wordpress/salty-wordpress-14-04-vbox-2014-07-12.box
An error occurred while downloading the remote file. The error
message, if any, is reproduced below. Please fix this error and try
again.
Just for the records: This is related to an issue in Vagrant 1.8.7. Downgrading to 1.8.6 made the trick but there's a newer Vagrant version (currently 1.9.5) so upgrading might work as well.
First-time setup, cannot get the VirtualBox:
No further message is displayed.