title: cannot find module css-loader while doing ng build -prod with angular-cli@1.0.0-beta.21
body: <p>I have following package.json configuration</p>
  
  <pre><code>"dependencies": {
  "@angular/common": "2.2.1",
  "@angular/compiler": "2.2.1",
  "@angular/core": "2.2.1",
  "@angular/forms": "2.2.1",
  "@angular/http": "2.2.1",
  "@angular/platform-browser": "2.2.1",
  "@angular/platform-browser-dynamic": "2.2.1",
  "@angular/router": "3.2.1",
  "@angular2-material/button": "^2.0.0-alpha.8-2",
  "@angular2-material/button-toggle": "^2.0.0-alpha.8-2",
  "@angular2-material/card": "^2.0.0-alpha.8-2",
  "@angular2-material/checkbox": "^2.0.0-alpha.8-2",
  "@angular2-material/core": "^2.0.0-alpha.8-2",
  "@angular2-material/grid-list": "^2.0.0-alpha.8-2",
  "@angular2-material/icon": "^2.0.0-alpha.8-2",
  "@angular2-material/input": "^2.0.0-alpha.8-2",
  "@angular2-material/list": "^2.0.0-alpha.8-2",
  "@angular2-material/menu": "^2.0.0-alpha.8-2",
  "@angular2-material/progress-bar": "^2.0.0-alpha.8-2",
  "@angular2-material/progress-circle": "^2.0.0-alpha.8-2",
  "@angular2-material/radio": "^2.0.0-alpha.8-2",
  "@angular2-material/sidenav": "^2.0.0-alpha.8-2",
  "@angular2-material/slide-toggle": "^2.0.0-alpha.8-2",
  "@angular2-material/slider": "^2.0.0-alpha.8-2",
  "@angular2-material/tabs": "^2.0.0-alpha.8-2",
  "@angular2-material/toolbar": "^2.0.0-alpha.8-2",
  "@angular2-material/tooltip": "^2.0.0-alpha.8-2",
  "ng2-material-dropdown":"0.5.4",
  "ng2-toasty": "^2.2.2",
  "@types/hammerjs": "^2.0.30",
  "angular2-cookie": "1.2.3",
  "angular2-material-datepicker": "^0.5.0",
  "angulartics2": "^1.1.9",
  "core-js": "^2.4.1",
  "d3": "^4.3.0",
  "es6-shim": "0.35.1",
  "ng2-datetime-picker": "^0.11.3",
  "ng2-tag-input": "0.6.0",
  "ng2-auto-complete":"0.8.2",
  "reflect-metadata": "0.1.3",
  "rickshaw": "^1.6.0",
  "rxjs": "5.0.0-beta.12",
  "ts-helpers": "^1.1.1",
  "zone.js": "^0.6.23",
  "ng2-file-upload": "^1.1.4-2",
  "angular2-color-picker": "^1.3.0",
  "@ng-bootstrap/ng-bootstrap": "1.0.0-alpha.16"
    },
    "devDependencies": {
  "@types/jasmine": "^2.2.30",
  "angular-cli": "1.0.0-beta.21",
  "codelyzer": "~0.0.26",
  "jasmine-core": "2.4.1",
  "jasmine-spec-reporter": "2.5.0",
  "karma": "1.2.0",
  "karma-chrome-launcher": "^2.0.0",
  "karma-cli": "^1.0.1",
  "karma-jasmine": "^1.0.2",
  "karma-remap-istanbul": "^0.2.1",
  "protractor": "4.0.5",
  "ts-node": "1.2.1",
  "tslint": "3.13.0",
  "typescript": "2.0.2",
  "typings": "1.3.1"
  </code></pre>
  
  <p>}</p>
  
  <p><code>ng build -prod</code> was working fine, however all of a sudden the same configuration gives the following error</p>
  
  <pre><code>ERROR in ./src/styles.css
  Module build failed: Error: Cannot find module '/Volumes/DATA/new-    clone-test/nbw/node_modules/css-loader/index.js?sourcemap&amp;minimize'
  at Function.Module._resolveFilename (module.js:440:15)
  at Function.Module._load (module.js:388:25)
  at Module.require (module.js:468:17)
  at require (internal/module.js:20:19)
  at loadLoader (/Volumes/DATA/new-clone-test/nbw/node_modules/loader-runner/lib/loadLoader.js:13:17)
  </code></pre>
  
  <p>I am not sure what causes this issue. Any help will be much appreciated. </p>