Have you tried clearing the cache? If the cache fills up, old files have to be removed before new ones can be loaded and that takes extra time. Have you tried the whole standard diagnostic? http://kb.mozillazine.org/Standard_diagnostic_-_Firefox

I have used every protocol Mozilla has suggested - including clearing the cache - and it does not cure the problem.

I now have to use a different browser, while my preferred browser is FireFox.

From what I have read online, this problem is widespread.

Create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test to see if this helps.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/

I had actually removed/uninstalled Firefox and installed a new version without using any of my old files or profiles and the newly installed version does not work either.

hello, maybe it's an issue with the protected mode in the flash plugin - you could try if disabling protected mode makes a difference.

Tried it before when I tried EVERYTHING that Mozilla suggested. Does not fix the problem.

does youtube work when you enable the html5 player?
www.youtube.com/html5

Try to disable hardware acceleration in Firefox (you need to close and restart Firefox).

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes