Dear all, Pretty much the same as mentioned here: https://support.mozilla.org/en-US/questions/1299343 The video in that link explains it. The menu bar keeps appearing/disappearing at a high frequency, randomly - and a key press will stop the glitch for a few seconds - or when firefox is not in focus. Tried cleaning, removing, without pluggins, setting the ui.key.menuAccessKeyFocuses etc etc. Now running the Beta, still same problem. For a while I suspected iCue and Corsair Strafe keyboard - or USB settings, ports, but nothing obvious. Also weird only Firefox suffers from it in that case. The weird thing is it can go ok for 4-5 hours but then the next day it's back again - once in this state it's unusable. Any help would be greatly appreciated, Best, Alex