Comment 59 for bug 1314556

Even more funny, with kernel 3.17 Firefox stopped hanging the on the page I have linked above http://www.howtogeek.com/196655/how-to-configure-the-grub2-boot-loaders-settings/ (on kernels starting from 3.18-rc1 the whole application would hang after few seconds during loading this page).

This looks like offtopic, but probably would help to track the original problem. I would think of a hang/freeze problem in some kind of messaging subsystem inside the kernel, which would give unpredictable random hangs in visually different and absolutely non-connected parts of the system (firefox/keyboard switcher,MTP/ADB devices).