Right now, running locally, every action from the Meteor CLI in OSX throws this exception:
/Users/mallorym/.meteor/packages/meteor-tool/.1.1.3.1d614zp
With a little help from here, I was able to fix it, and without having to delete all my downloaded meteor packages, as suggested in that post. It was enough to delete the metadata:
rm -rf ~/.meteor/package-metadata
Just be prepared to wait quite a while while meteor recreates these databases on next start.