If you are getting the bellow error on a recent version npm (1.4~)
npm ERR! cb() never called! npm ERR! not ok code 0
Chances are you are facing this issue:
npm shrinkwrap install - npm ERR! cb() never called! (Linux / OS X) https://github.com/npm/npm/issues/5920
Unfortunently there is no fix avialable as of yet (29th Oct 2014). The only solution seems to be rolling back to a old version of npm unaffected by the bug.
The above version is not affected. You can downgrade npm using it self :)
sudo npm install email@example.com -g