npm install module Error: tunneling socket error

I am not able to install nodejs modules using npm on windows. I am behind a proxy and I set the proxy like this:

npm config set proxy internet.cp:8080
npm config set proxy-http internet.cp:8080

When I try to install a packet, i get this error:

npm info retry will retry, error on last attempt: Error: tunneling socket could not be established

I have some questions:

 - how can I make npm work with socks5
 - can I configure a proxycap file so that npm will use socks5
 - other suggestions

via georgiana_e