Today, in the middle of development, react-native started throwing "Error: Cannot find module '...." errors for all projects (even new ones).
I followed the usual steps (watchman del, clearing npm cache, etc..) to no avail. I then decided to uninstall & re-isntall node, npm, react-native...again to no avail.
Here are the steps to reproduce my issue:

react-native init myApp
cd myApp
react-native run-ios

After uninstalling node, npm and removing all node modules, the projects started working again.