I got this issue when following the Angular Heroes tutorial. It was caused by invalid location of the angular-in-memory-web-api import, in the systemjs.config.js file. The correct location should be :
'angular-in-memory-web-api': 'npm:angular-in-memory-web-api/bundles/in-memory-web-api.umd.js'
and remove packages.angular-in-memory-web-api
see https://github.com/angular/quickstart/commit/541bdc5f634e1142860c56cace247234edfaf74b