Error on live generating angular2-polyfills.js and app.bundle.js

I am using 2.0.0-beta.24 and got some error just today. I used:

ionic start FormValidation blank --v2 --ts

After ionic serve and when I change any file, I got both files 404 and blank page:

GET http://localhost:8100/build/js/angular2-polyfills.js 
GET http://localhost:8100/build/js/app.bundle.js 

Basically the www/build/js didn’t get built. I only saw this during the first run:

TypeScript error: /Users/myusername/Documents/MyFormValidation/node_modules/angular2/src/facade/promise.d.ts(1,10): Error TS2661: Cannot re-export name that is not defined in the module.

When I change a file, I saw this:

ionic $ [00:26:36] Starting 'clean'...
[00:26:36] Finished 'clean' after 11 ms
[00:26:36] Starting 'html'...
[00:26:36] Finished 'html' after 9.65 ms
HTML changed: www/build/pages/home/home.html

This is a “silent” failure because it shows me no error anywhere, even with server log enabled.

This also happens when I downgraded to beta 21. So it must be something to do with the server or start templates on 4/5/2016.

Can someone help?

This error is mysterious disappeared today!

Scary indeed!