Linux, firefox 50.0.1 This only happens when devtools is docked and stopped at a javascript breakpoint. Keyboard function keys F8, F10, F11, and F12 work but the mouse buttons do not anywhere in the browser window. When the devtools are undocked, I can click on the run triangle normally. Safe-mode makes no difference. Everything works fine if I open firefox as a different user. Here is the last backtrace. A coding exception was thrown in a Promise resolution callback. See https://developer.mozilla.org/Mozilla/JavaScript_code_modules/Promise.jsm/Promise Full message: TypeError: eventLoop is undefined Full stack: ThreadActor<._popThreadPause@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/script.js:536:5 ThreadActor<.onResume/<@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/script.js:1019:7 Handler.prototype.process@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:937:23 this.PromiseWalker.walkerLoop@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:816:7 this.PromiseWalker.scheduleWalkerLoop/<@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:750:11 Spinner.prototype.observe@resource://gre/modules/AsyncShutdown.jsm:551:9 EventLoop.prototype.enter@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/script.js:348:5 ThreadActor<._pushThreadPause@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/script.js:531:5 ThreadActor<._pauseAndRespond@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/script.js:739:7 BreakpointActor<.hit@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/breakpoint.js:172:12 @http://selp.bethechange.test/signup.js:37:14 r.event.dispatch@http://selp.bethechange.test/jquery.min.js:3:9804 r.event.add/q.handle@http://selp.bethechange.test/jquery.min.js:3:7866