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
• Hitman Pro
• ESET Online Scanner

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.

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Tive esse mesmo problema é um spyware.

Verifique se seu Windows Defender está desativado!

http://windows.microsoft.com/pt-br/windows-vista/scan-for-spyware-and-other-potentially-unwanted-software

Possa ser que funcione ;)

can you send the english version please

http://windows.microsoft.com/en-us/windows-vista/scan-for-spyware-and-other-potentially-unwanted-software

English version

Thanks for information but I cannot open or even locate windows defender. The search in 'settings' informs me that windows defender has been turned off but there doesn't appear to be a way to turn it back on. There is no icon on the bottom task bar nor does it appear in the control panel (My PC is All in One running Windows 8 bought new in February 2013)

I am signed in as administrator.

Could it be that my AVG has turned it off or it was never installed in the first place?.

Hi, may you please use the extra tools as i stated in my first post.

Will do and thanks.

Sorry, next post in your language. ;)

Strange... Windows 8 comes with its own integrated antivirus software: Windows Defender

Exellent solution Waka_Flocka_Flam!