out of no where, suddenly getting __webpack_require__.h is not a function

My app was working fine... Attempted to run my feature specs using capybara with chrome (apparition driver), and I got: Failed to compile webpack!

I then launched my app in the browser, which was working totally fine yesterday, and I get a broken app with a js error:

index.js:37 Uncaught TypeError: __webpack_require__.h is not a function
    at Module../node_modules/webpack-dev-server/client/index.js?protocol=ws%3A&hostname=localhost&port=3035&pathname=%2Fws&logging=info&reconnect=10 (index.js:37:1)
    at __webpack_require__ (bootstrap:19:1)
    at __webpack_exec__ (external var "AppConfiguration":1:1)
    at external var "AppConfiguration":1:1
    at Function.__webpack_require__.O (chunk loaded:25:1)
    at external var "AppConfiguration":1:1
    at webpackJsonpCallback (jsonp chunk loading:32:1)
    at app.js:1:67
./node_modules/webpack-dev-server/client/index.js?protocol=ws%3A&hostname=localhost&port=3035&pathname=%2Fws&logging=info&reconnect=10 @ index.js:37
__webpack_require__ @ bootstrap:19
__webpack_exec__ @ external var "AppConfiguration":1
(anonymous) @ external var "AppConfiguration":1
__webpack_require__.O @ chunk loaded:25
(anonymous) @ external var "AppConfiguration":1
webpackJsonpCallback @ jsonp chunk loading:32
(anonymous) @ app.js:1

If I open an incognito window and visit my app, everything works FINE...

No incognito window.. totally busted.

Total nonsense.

...

I delete my cookies, local storage, session storage for localhost.. deleted public/packs, ran rake tmp:clear Same thing.. Busted when not in an incognito window... Out of no where... No code changes, nothing...