Resolved - The cert was rolled back by npm, which resolves the SSL errors faced earlier. If you have any further issues, please open a support ticket.
Mar 2, 20:22 UTC

Identified - The self-signed certificate for npm (Node.js Package Manager) is no longer valid, causing SSL errors for requests to https://registry.npmjs.org and affecting npm installations. We are aware of the issue and working on a permanent solution, in the meantime the issue can be bypassed by connecting to the relevant instances via SSH and running the command ' sudo /opt/nodejs/0.8.11/bin/node /usr/bin/npm config set ca "" ', then running an 'Apply' via the environment page of the Engine Yard dashboard to re-run the instance configuration.
Feb 28, 12:57 UTC