ConcurrentCompilationError

I am very new to Aurelia, just followed http://aurelia.io/docs/tutorials/creating-a-contact-manager

While running the code using

au run getting below error message, ( i am sure running once only)

「wdm」: ConcurrentCompilationError: You ran Webpack twice. Each instance only supports a single concurrent compilation at a time.
at Compiler.run (C:\Personal\aureliaProj\firstAUProj\node_modules\webpack\lib\Compiler.js:149:37)
at rebuild (C:\Personal\aureliaProj\firstAUProj\node_modules\webpack-dev-server\node_modules\webpack-dev-middleware\lib\context.js:81:24)
at done (C:\Personal\aureliaProj\firstAUProj\node_modules\webpack-dev-server\node_modules\webpack-dev-middleware\lib\context.js:59:7)
at AsyncSeriesHook.eval [as callAsync] (eval at create (C:\Personal\aureliaProj\firstAUProj\node_modules\tapable\lib\HookCodeFactory.js:24:12), :18:1)
at AsyncSeriesHook.lazyCompileHook [as _callAsync] (C:\Personal\aureliaProj\firstAUProj\node_modules\tapable\lib\Hook.js:35:21)
at emitRecords.err (C:\Personal\aureliaProj\firstAUProj\node_modules\webpack\lib\Compiler.js:201:22)
at Compiler.emitRecords (C:\Personal\aureliaProj\firstAUProj\node_modules\webpack\lib\Compiler.js:313:39)
at emitAssets.err (C:\Personal\aureliaProj\firstAUProj\node_modules\webpack\lib\Compiler.js:195:10)
at hooks.afterEmit.callAsync.err (C:\Personal\aureliaProj\firstAUProj\node_modules\webpack\lib\Compiler.js:299:14)
at AsyncSeriesHook.eval [as callAsync] (eval at create (C:\Personal\aureliaProj\firstAUProj\node_modules\tapable\lib\HookCodeFactory.js:24:12), :15:1)
at AsyncSeriesHook.lazyCompileHook [as _callAsync] (C:\Personal\aureliaProj\firstAUProj\node_modules\tapable\lib\Hook.js:35:21)
at asyncLib.forEach.err (C:\Personal\aureliaProj\firstAUProj\node_modules\webpack\lib\Compiler.js:296:27)
at done (C:\Personal\aureliaProj\firstAUProj\node_modules\neo-async\async.js:2809:11)
at C:\Personal\aureliaProj\firstAUProj\node_modules\neo-async\async.js:2760:7
at MemoryFileSystem.writeFile (C:\Personal\aureliaProj\firstAUProj\node_modules\memory-fs\lib\MemoryFileSystem.js:328:9)
at writeOut (C:\Personal\aureliaProj\firstAUProj\node_modules\webpack\lib\Compiler.js:282:29)

But, when use au run --watch, without error the application came up.

Is there any possibility to suggest me on this error message.?