It's possible that you are having a problem with some Firefox add-on that is hindering your Firefox's normal behavior. Have you tried disabling all add-ons (just to check), to see if Firefox goes back to normal?

Whenever you have a problem with Firefox, whatever it is, you should make sure it's not caused by one (or more than one) of your installed add-ons, be it an extension, a theme or a plugin. To do that easily and cleanly, run Firefox in safe mode (don't forget to select Disable all add-ons when you start safe mode). If the problem disappears, you know it's from an add-on. Disable them all in normal mode, and enable them one at a time until you find the source of the problem. See this article for information about troubleshooting extensions and themes and this one for plugins.

If you need support for one of your add-ons, you'll have to contact its author.

If the problem does not disappear when all add-ons are disabled, please tell me, so we can work from there. Please have no fear of following my instructions to the line, as all can be easily undone.

Thank you for the reply I am running in safe mode as I write, with all add-ons disabled. The time to load a page has only improved by approx 5 seconds. I recently changed to v3.6.8 and this is when I noticed the slowdown. However, on rolling back to previous versions (which ran before with no problems), the slow load time remains. As far as I can tell, everything else on the computer is the same. Antivirus/malware scans report no issues as does the firewall (Avast). I have a 3.5Mb/s average download speed which is stable.

RichJ

Thank you for the reply I am running in safe mode as I write, with all add-ons disabled. The time to load a page has only improved by approx 5 seconds. I recently changed to v3.6.8 and this is when I noticed the slowdown. However, on rolling back to previous versions (which ran before with no problems), the slow load time remains. As far as I can tell, everything else on the computer is the same. Antivirus/malware scans report no issues as does the firewall (Zone Alarm). I have a 3.5Mb/s average download speed which is stable.

RichJ

A possible cause is security software (firewall) that blocks or restricts Firefox without informing you about that, possibly after detecting changes (update) to the Firefox program.
Remove all rules for Firefox from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox.
See Server Not Found - Troubleshoot connection problems and Configure firewalls so that Firefox can access the Internet and http://kb.mozillazine.org/Firewalls

Hi and thank you.

I disabled ZoneAlarm completely for the purposes of testing but the opening speed (to show homepage - google) is still slow. There is a little improvement when opening bookmarked pages and navigating within sites, but speed is still poor compared with before.

Running in safe mode (all add-ons disabled) makes no appreciable difference.

RichJ

Update

Everything appears to be back to normal with my favourite browser! I did a thorough clean-out of all things FF and d/l'd a fresh version of 3.6.8 and all appears to be well.

Thank you to everyone who replied

RichJ