Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

I restarted Firefox in Safe Mode, exited, and then restarted again. Now no sign of random black boxes. Many thanks, your help is much appreciated.

Glad to help. Safe Surfing.

tontoe said

The address bar text is blacked out - can see bits of gray text. Also, I get random black boxes appearing on pages and in fill-in fields Text on the settings page is almost completely obscured And as an example, the data in the Troubleshooting Information sction below this is randomly blacked out I've tried changing the theme, and also turning off hardware acceleration. This was all happening before I added Privacy Badger Can anybody help? Thanks

Starting in safe mode seems to help but it is not a permanent solution unless you want to start in safe mode all the time. Instead go to Options, General, and Performance. At Use recommended Performance Settings there may be a check mark. If so deselect that by clicking on it. A dialog menu will pop up with Use Acceleration Hardware. Deselect that. That should fix your problem