Forever "Not Responding" if certain actions are performed.

Question

Whenever I perform one of these three actions...
{A} Attempt to open Browser Settings
{B} Attempt to UP-load a file of any kind
{B} Attempt to DOWN-load a file of any kind
...Firefox instead goes all "Not Responding" and never comes out. I've even left it to sit for a night and when I came back nothing had changed.
I've always cleared my Download History, and any options regarding Browser Settings is not an option.
Any ideas?

Answer 1

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test.
*http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
Do a malware check with several malware scanning programs on the Windows computer.
Please scan with all programs because each program detects different malware.
All these programs have free versions.
Make sure that you update each program to get the latest version of their databases before doing a scan.
*Malwarebytes' Anti-Malware:<br>http://www.malwarebytes.org/mbam.php
*AdwCleaner:<br>http://www.bleepingcomputer.com/download/adwcleaner/<br>http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
*SuperAntispyware:<br>http://www.superantispyware.com/
*Microsoft Safety Scanner:<br>http://www.microsoft.com/security/scanner/en-us/default.aspx
*Windows Defender:<br>http://windows.microsoft.com/en-us/windows/using-defender
*Spybot Search & Destroy:<br>http://www.safer-networking.org/en/index.html
*Kasperky Free Security Scan:<br>http://www.kaspersky.com/security-scan
You can also do a check for a rootkit infection with TDSSKiller.
*Anti-rootkit utility TDSSKiller:<br>http://support.kaspersky.com/5350?el=88446
See also:
*"Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked
*https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware