I ran into an issue today on the vagrant IonicBox when I tried to create a new Ionic project at work behind the firewall/proxy even with all of the configurations for npm, git, bower, and bash setup for the proxy as detailed at proxy-configurations.
Luckily, Ionic had a fix for this already.
Linux
All I had to do was put PROXY=http://myserver:myport in front of the ionic start command.
PROXY=http://myserver:myport ionic start todo blank
Windows
When you are using npm, bower, and git behind a proxy server you have to do a little bit of configuration. Luckily it is super easy to do these configurations. Almost all of the programs have command line commands to set and unset the proxy server.
set http_proxy=[Your Proxy]:[Proxy Port]
set https_proxy=[Your Proxy]:[Proxy Port]
set http_proxy=
set https_proxy=
Run from an administrative command prompt