I have this problem too. Additionally I notice that if I duplicate the tab (I'm using tab mix plus) the duplicated tab does not do this. The original tab will still say "Connecting..." but the duplicated tab won't, even though both tabs are displaying the exact same content.

Clear Cookies & Cache

• https://support.mozilla.com/en-US/kb/Template:clearCookiesCache

Clear the Network Cache

• https://support.mozilla.com/en-US/kb/How%20to%20clear%20the%20cache#w_clear-the-cache

Troubleshooting extensions and themes

• https://support.mozilla.com/en-US/kb/Troubleshooting%20extensions%20and%20themes

Check and tell if its working

BTW your Flash plugin is quite older. You need to update it.

Adobe Flash Player 10.3.183.7 (2.94 MB)

• http://get.adobe.com/flashplayer/

When Downloading Plugins Update setup files, Remove Checkmark from Downloading other Optional Softwares with your Plugins (e.g. Toolbars, McAfee, Google Chrome, etc.)

Update All your Firefox Plugins

• https://www-trunk.stage.mozilla.com/en-US/plugincheck/
• http://www.mozilla.com/en-US/plugincheck/

A possible cause is security software (firewall) that blocks or restricts Firefox or the plugin-container process without informing you, 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 and the plugin-container process and the updater process.

See:

• https://support.mozilla.com/kb/Server+not+found
• https://support.mozilla.com/kb/Firewalls