Why does Firefox 'grey-out' and stop working and then the color scheme becomes normal and resumes working? This grey-out period can last from 10-60 seconds. Hardware includes HP 8440p with 8GB RAM and SSD. I would think that this configuration / model is well suited for 16.04: the system monitor indicates that 20% of RAM is used, with Firefox has ~5 windows
UPDATE:
The upgrade to Firefox Quantum has resolved the overheating, speed and freezing issue.