Try running Firefox in Diagnose Firefox issues using Troubleshoot Mode. If it functions properly in that configuration, then one of your add-ons is the culprit.

Also, if you have some kind of security software installed which scans links like AVG Safe Search, AVG Link Scanner, McAfee Secure Search, McAfee Site Advisor, or some other kind of anti-phishing tool, try disabling it.

Thanks, Xircal, I ran Firefox in safe mode and that did fix the problem. How do I know what add-ons I have, and which one is the culprit? I use Bullguard and have never had any problem with it and can conclude that it isn't the problem.

They're listed in Tools | Add-ons | Extensions.

What you'll have to do is to restart in Safe Mode again, then checkmark "Disable All Add-ons". Then click the button "Make changes and restart".

Next, go the the Extensions menu described above and re-enable them one-by-one until the problem recurs. Then you'll know which one is the culprit.

You could try disabling that Bullguard to begin with.

This happens to me all the time. On Facebook I cannot scroll without ff hanging up. It is so annoying that I uninstalled and re-installed. Still nothing changed. It was happening on the older version and then I did a windows update and got better, then ff4 updated and I'm back to the same problem. If this doesn't get better I will uninstall and leave it off. I am not going to run ff in safe mode either. This needs to be fixed.

I have cable. So it's not the internet connection.

@ dbrobinsonii, You can return Firefox to its default settings by starting in Safe Mode, then checkmark the option called Reset all user preferences to Firefox defaults.

Then click the button called Make Changes and Restart.

You will however lose any customizations you made.

I don't really understand why any of this should be necessary, surely a fresh download, fresh install, and only adopting recommended or certified extensions and/or add-ons should result a stable piece of software?