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

Reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• Press and hold Shift and left-click the Reload button.
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Command + Shift + R" (Mac)

Clear the cache and the cookies from sites 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"

Thanks for the advise. I already tried Safe Mode and the problem persists though...

Thanks also Cor-el. I just recently cleared 'Everything' from my history so I am not currently experiencing the problem. It should come back shortly, when it does I'll try your solutions.

Maybe I'm wrong but by the sounds of it what you're suggesting are just temporary fixes? Like would I continuously have to bypass or clear the cache to avoid the problem occurring? Or would I have to 'remove cookies' from each site that incurs the problem?

Yes, a reload and bypassing the cache or clearing the cache and cookies is a temporary fix for issues like this, but is usually sufficient to recover.

It shouldn't be necessary often do to this and if this happens a lot then you may have a connection problem or possibly you have security software (firewall, anti-virus) that is interfering.

It's just strange because I've never experienced this problem before. I've no new software installed so maybe it is something to do with the internet provider. Thanks again for your help.

Hello,

The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Note: This will cause you to lose any Extensions, Open websites, and some Preferences.

To Reset Firefox do the following:

1. Go to Firefox > Help > Troubleshooting Information.
2. Click the "Reset Firefox" button.
3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
4. Firefox will open with all factory defaults applied.

Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

Thank you.

I've been experiencing the problem on a brand new laptop, so my firefox more or less has factory settings. It's been happening to this and an older laptop of mine. And I was using Chrome yesterday and the same thing happened strangely enough. The fact that it has never happened until I switched my internet provider suggests to me that it's something to do with them. Thanks for the advice.

Note that information in the cache and cookies may get invalid if you change the ISP and get another IP address and DNS servers.
In cases like that you may need to clear the entire cache and all the cookies to reset data stored from web servers.

I cleared the cache using the method you described above and cookies by clearing 'Everything' from my history. Is that OK?

Yes, that should be OK.

Do you still experience those problems?