npm cache cleanfirst.
If that doesn’t fix things, take a look in
%APPDATA%\npm-cache, or if you’re using PowerShell,
After cleaning the cache, you may still be left with remnants. Manually remove everything in that directory, and try again. This has always fixed things for me.
As @Crazzymatt was mentioning, as of MPM 5 version, we need to use
npm cache verify instead of
npm cache clean. Or else you will get an error as preceding.