Check for malware and disable all addons by troubleshooting in safe mode. CHECK FOR MALWARE WITH ALL PROGRAMS linked below, they scan for different malware, make sure you update all definitions (malwarebytes) and run full scans, not quick scans. * [http://www.microsoft.com/security/scanner/default.aspx Microsoft Safety Scanner] * [http://www.malwarebytes.org/products/malwarebytes_free/ MalwareBytes' Anti-Malware] * [http://support.kaspersky.com/faq/?qid=208283363 TDSSKiller - AntiRootkit Utility] * [http://www.surfright.nl/en/hitmanpro/ Hitman Pro] * [http://www.eset.com/us/online-scanner/ ESET Online Scanner] [http://windows.microsoft.com/MSE Microsoft Security Essentials] is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one. SAFE MODE Further information can be found in the [[Troubleshoot Firefox issues caused by malware]] article. ''(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 [[Troubleshooting extensions and themes]] article for that.

I have a problem with pop-up. too

Hi larryruffin, you have a problem with a popup promoting a particular download? I suggest trying the links in the above post: https://support.mozilla.org/en-US/questions/971175#answer-479066