Windows 10 v1909, Firefox 77.0.1

Firefox on my desktop started loading pages really slowly. Even the Google home page was taking 10 minutes or more to load. Firefox on my laptop was running OK. Then a week later Firefox on my laptop started loading pages slowly.

I tried the following:
Help > Rstart with Add-ons disabled
Help > Troubleshooting Information > Refresh Firefox
Reinstall Firefox
Reinstall Adobe Reader DC

Nothing seemed to help.

I finally found a solution that worked with both my desktop and laptop:
Uninstall Adobe Reader DC
Reinstall Adobe Reader DC

Firefox now loads web pages normally