My headaches described below were due to my npm module’s dependency clauses’ versioning stanzas. I had set dependencies to automatically update but clipped them to the current minor version. Eventually they got crusty, and npm actually stopped finding the versions I was demanding in a speedy fashion. Both edges of the upgrade knife can cut you, don’t let dependencies get too old. 🙂 Fuller explanation on SO.
Historical blathering follows… (continued…)