Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

To Enable SafeMode

• You can open Firefox 4.0+ in Safe Mode by holding the Shift key when you open the Firefox desktop or Start menu shortcut.
• Or open the Help menu and click on the Restart with Add-ons Disabled... menu item while Firefox is running.
• Once you get the pop-up, just select "'Start in Safe Mode"

If it works in Safe Mode and in normal mode with all extensions (Tools > Add-ons > Extensions) disabled then try to find which extension is causing it by enabling one extension at a time until the problem reappears.

Close and restart Firefox after each change via "Firefox > Exit" (Windows: Firefox/File > Exit; Mac: "Firefox > Quit Firefox"; Linux: "Firefox/File > Quit")

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Clear the cache and the cookies from websites that cause problems.

"Clear the Cache":

• Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Firefox/Tools > Options > Privacy > Cookies: "Show Cookies"

I said straight away I've cleared the cache and removed cookies. I also said I've loaded firefox in safe mode and still the problem remains.

If clearing cookies doesn't work then it is possible that the cookies.sqlite file that stores the cookies is corrupted.

Rename (or delete) cookies.sqlite (cookies.sqlite.old) and delete other present cookie files like cookies.sqlite-journal in the Firefox profile folder in case the file cookies.sqlite got corrupted.

• http://kb.mozillazine.org/Cookies
• https://support.mozilla.org/kb/Deleting+cookies

You can also try if it works in a Private Browsing mode window (Firefox > New Private Window).

Also fails under Win7 Firefox 22.0 with cache cleared using a Private Browsing mode window

Regards

You can try to reset (power off/on) the router.

See also:

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

I have the same problem on a new Windows 8 HP desktop. I have done all of the above; completely unistalled FF twice. On the second installation, went down to FF v21 - still does not work (but works in Chrome)

Nothing? seriously?

It looks like quite a few people are having this issue, and number of tickets on this forum have been opened...

Well after week with this problem, trying all things read, I connect my speakers, and "wallaaaa" all is working now. Incredible but it work for me

yeah, it 'suddenly' started working for me too