Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• TDSSKiller - AntiRootkit Utility

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

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

Thank you for your response. I use Microsoft Security Essentials and Avast as my primary troubleshooters and they didn't pick up anything. On an as needed basis, I used Super Malwarebytes, Malwarebytes, stinger, Advanced system care, and downloaded and used Microsoft Safety Scanner. None of them showed any signs of malware or a virus.

Just all of a sudden, I noticed when I signed off Mozilla Firefox that I had another window open that remained on my PC. First it was for Rewardzoneusa.com and now, occassionaly, Brazilwoman or something like that. In both cases, I select the red X to close the application & Window, then I'm asked to confirm that I want to allow the page to shut down. A Real Pain in the you know what.

I have even run a complete uninstall & reinstall of Mozilla Firefox. The problem doesn't appear every time I run Firefox, but enough to be a real pain.

Thanks for Trying.

Harris

Try Firefox Safe Mode to see if the problem goes away. Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

• 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 the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help other users who have the same problem.