Clear all cookies, all of them. In the Privacy tab of the Firefox Options/Preferences please clear all cookies from this menu. Corrupt cookies sometimes wedge their way into the Profile of the current user.

Please also try a new profile folderUse multiple profiles in Thunderbird.

Please post back with the results!

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).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can check the permissions for the domain in the currently selected tab via these steps:

• Click the "Site Identity Button" (globe/padlock) on the location bar
• Click "More Information" to open "Tools > Page Info" with the Security tab selected
• Go to the Permissions tab (Tools > Page Info > Permissions) to check the permissions for the domain in the currently selected tab

I might've failed to mention it but I did remove all cookies. The Firefox is literally a fresh install with a few add-ons that I use. And as far as I'm aware, I'm not using a Profile as I don't believe I have Thunderbird installed.

I'm going to work on the other solution and post back with the results. Thank you very much though :)

In Safe Mode, I'm still unable to log-in as the problem has now extended to being able to access YouTube at all. I checked again and I'm able to access YouTube on my other browser (Torch/Google Chrome) and can log in with no problems. The page stays white and the page continuously loads.

Looking at the Permissions tab, everything appears to have permissions but it is all set to "Use Default" which should be for the website to be able to use it. Is there some specific setting I should use for the website for me to be able to access it?

The problem seems to have resolved itself somehow. I haven't done anything different after trying to fix this problem far back at the beginning and running a couple of scans in between then and now that found the usual cookies from my websites that had been cleared when I complained of this problem in the first place. I'm really hoping that it doesn't start again.

Syraphia, I am marking your last comment as solved, however if it comes back and starts to act again please start a new thread with reference to this one if needed.

Thank you!

I also have this problem. I thought it might be a virus or something, but none of my security software found anything. I tried every solution listed above. Nothing. I wound up reformatting the computer. Still have the problem. Obviously it's something in Firefox. IE works fine.