edit fix found! You could downgrade, but it would be recommended that you downgrade to Firefox 3.6 as that is still supported, whereas Firefox 5 and 6 are not.

• see installing a previous version of firefox

Any problem is quite likely to be related to the plugins or add-ons that you use rather than to Firefox itself. Such problems are often quite specific to the setup and combinations of software extensions used, so if you do have a problem with Firefox not responding it may help to start your own thread with full details of your own setup.

If you are getting a message saying it is not responding then probably nothing is actually crashing.

If you do get a crash it could be (in order of severity)

• your OS: Windows that crashes,
• the Firefox Browser itself,
• or a Firefox process running as a plugin container.

Firefox itself is usually quite stable and responsive. (You appear to be using a 64 bit computer system, so problems are unlikely to relate to the machine not meeting Firefox minimum specs)

First of all try in firefox's safe mode but do not make changes when you get the check list just click on continue. If that fails to help, next try disabling or even uninstalling any plugins and themes. See troubleshooting plugins.

If all else fails fall back on the guide

• basic troubleshooting <-- blue clickable link --

Update
possible cause and workaround