This appears to be caused by a missing dependency when running vagrant 1.8.1 on Windows 10. It happened for me under windows command line "cmd.exe" and under git-bash. This was also reported and closed on the mitchellh/vagrant GitHub repo as "On Windows 10, "vagrant up" and "vagrant box add" throw blank errors #6852"
I and others worked around this by installing the "Microsoft Visual C++ 2010 SP1 Redistributable Package (x86)" as suggested by jeremywhittington in issue #6754.
A relevant snipped of the "vagrant --debug add hashicorp/precise32" output shows "curl" exiting with a strange code that doesn't get propagated to the standard vagrant output:
...
INFO subprocess: Starting process: ["C:\\HashiCorp\\Vagrant\\embedded\\bin/curl.EXE", "-I", "-q", "--fail", "--location", "--max-redirs", "10", "--user-agent", "Vagrant/1.8.1 (+https://www.vagrantup.com; ruby2.2.3)", "--continue-at", "-", "-H", "Accept:application/json", "https://atlas.hashicorp.com/hashicorp/precise32"]
DEBUG subprocess: Selecting on IO
DEBUG subprocess: Waiting for process to exit. Remaining to timeout: 32000
DEBUG subprocess: Exit status: 3221225781
WARN downloader: Downloader exit code: 3221225781
ERROR warden: Error occurred: The box 'hashicorp/precise32' could not be found or
could not be accessed in the remote catalog. If this is a private
box on HashiCorp's Atlas, please verify you're logged in via
`vagrant login`. Also, please double-check the name. The expanded
URL and error message are shown below:
URL: ["https://atlas.hashicorp.com/hashicorp/precise32"]
Error:
...