About how long is it before the problem starts? Are you looking at a normal webpage or a page with players?

You said the problem continues in Firefox Safe Mode.

Start your Computer in safe mode with network support. Then start Firefox. Try Secure websites. Is the problem still there?

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode Starting Any Computer In Safe Mode; Free Online Encyclopedia

What are you using as protection? Anti-virus, mal-scanners . . . . .

Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

Hello, Fred. The problem is on ANY site, secured or not, it just doesn't load. I have a few simple HTML and CSS pages, no JS or anything else, those doesn't load either. The problem started occuring since about 4-6 months ago, before version 56 (I ketp using v. 56 for some time to give chance for extension developers to catch up) sometimes once a week, sometimes 2-3 times per day. I'm using Avast Free as security. Also deleted Firefox from Firewall rules 2 times already. So sometimes Firefox is trusted and sometimes it's not? Isn't that weird? The only thing I didn't tested is restarting the computer in safe mode, but since the problem sometimes lasts for a couple of minutes, I don't know how concludent this would be.

In most computers, there are several types of Safe Mode. The primary ones used most are; *Safe Mode: Only programs that came with the computer are started. No other programs will be started unless the user starts them. *Safe Mode with Networking: Same as above but the network drivers (internet) will also be running. This is a way to test if one of the other programs on the computer is causing the issue.

Food for thought;

Install Older Version Of Firefox {web link} Be sure to read everything here.

If you still want to downgrade, look under; I still want to downgrade. Click the Directory of other versions and languages link. Look for the directory of the version that you want. But, remember that old versions may have security issues.

You should also check out Firefox; Extended Support Release {web link} ESR Notes System Requirements

I'm sorry Fred, but this is my workstation, I don't have the time for testing, I'm always on the clock. I was hoping someone else had this problem and, maybe, someone found a solution. However, I'm thinking that Windows itself may have something to do with it, as it's a quite old install and, in my experience, no matter how well you maintain a Windows install, it will eventually go slow and it will need a fresh install. Oh boy... I really miss my Linux days... Thank you for your time and interest.

Perform a System File Check to fix corrupted system files

Win 7, 8, 10, Vista: https://support.microsoft.com/en-us/kb/929833 Win XP: https://answers.microsoft.com/en-us/windows/forum/all/windows-xp-scan-and-fix-disk-errors/6fe2827a-4be6-4bc1-8083-5139b5aa3a3d

Wiki - Windows 10 System File Check http://answers.microsoft.com/en-us/windows/wiki/windows_10-update/system-file-check-sfc-scan-and-repair-system-files/bc609315-da1f-4775-812c-695b60477a93