Google uploaded an update to ChromeOS this week that was missing the "&" ampersand code, causing many Chromebooks out in the wild to be locked out of ChromeOS. This comes fresh off another update that left out the "%" sign, causing similar issues should your wifi network or password rely on it. Google didn't announce the problem, but it was ferreted out by a Reddit user this week. The only fix was to powerwash your Chromebook and start over. Google has since put out a new build to correct the oversight. It'll roll out over the next few days.