Hi raphael75, Please try a new profile or reset Firefox. It could be a stored preference affecting the performance if this also does not happen in other applications. 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: * [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/viruses/disinfection/5350 Anti-Rootkit Utility - TDSSKiller] * [http://general-changelog-team.fr/en/downloads/viewdownload/20-outils-de-xplode/2-adwcleaner AdwCleaner] (for more info, see this [http://www.bleepingcomputer.com/download/adwcleaner/ alternate AdwCleaner download page]) * [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. Further information can be found in the [[Troubleshoot Firefox issues caused by malware]] article. Did this fix your problems? Please report back to us!Hello, The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. <br> '''Note''': ''This will cause you to lose any Extensions and some Preferences.'' *Open websites will not be saved in Firefox versions lower than 25. To Reset Firefox do the following: '''For Firefox versions previous to 29.0:''' #Go to Firefox > Help > Troubleshooting Information. #Click the "Reset Firefox"[[Image:Button reset]] button. #Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish. #Firefox will open with all factory defaults applied. '''For Firefox 29.0 and above:''' #Click the menu button [[Image:New Fx Menu]], click help [[Image:Help-29]] and select ''Troubleshooting Information''.Now, a new tab containing your troubleshooting information should open. #At the top right corner of the page, you should see a button that says "Reset Firefox"[[Image:Button reset]]. Click on it. #Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish. #Firefox will open with all factory defaults applied. Further information can be found in the [[Reset Firefox – easily fix most problems]] article. Did this fix your problems? Please report back to us! Thank you.

Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem. *Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance *Do NOT click the Reset button on the Safe Mode start window *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes