Check your firewall/antivirus/security suite for settings that may be causing this. If that's not it, 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.

Antivirus and the like don't cause this, I have checked. It's not caused by add-on/plug-in either, I have tested with Safe Mode. It's still happening with or without them.

Can you please try it in a new (temporary) Firefox profile and see if the issue is still present? See this article to know how to create a new Firefox profile. Please report back the results.

Your above posted system details show outdated plugin(s) with known security and stability risks.

• Next Generation Java Plug-in 1.6.0_15 for Mozilla browsers

Update the Java plugin to the latest version.

• http://java.sun.com/javase/downloads/index.jsp (Java Platform: Download JRE)

See also:

• http://kb.mozillazine.org/Error_loading_websites
• http://kb.mozillazine.org/Browser_will_not_start_up