Firefox gives a can't read source file message when downloading

Question

I have tried to download and install the Opera browser and other .exe files (because Firefox is not working correctly, as witnessed by this message). First, I have to pause and restart the downloads many times; second, after the download is apparently complete, I get the "source file could not be read". I don't know whether it is related, but pages rarely complete opening and require that I stop the loading process.
I clicked to add troubleshooting information and couldn't do it. Connection failure with Mozilla.
?????

Answer 1

Did you check your security software?
Boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.
*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