That is a problem with JavaScript garbage collection (GC; memory cleanup). *Firefox 41.0 Crash Report [@ js::GCMarker::processMarkStackTop(js::SliceBudget&) ] Such issues are usually hard to track down because they happen when a component tries to access memory that has been released via GC, so this location no longer exists. ---- Can you give more details when these crashes happen? Try to create a new profile as a test to check if your current profile is causing the problem. See "Creating a profile": *https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles *http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems. *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox You can also do a malware check with several malware scanning programs on the Windows computer. *https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware 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 ----- You can check for problems with current Shockwave Flash plugin versions and try this: *make sure you have the latest Flash version:<br>http://www.adobe.com/special/products/flashplayer/fp_distribution3.html *check for updates for your graphics drive drivers<br>https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration *disable protected mode in the Flash plugin (Windows Vista and later)<br>https://support.mozilla.org/kb/adobe-flash-protected-mode-firefox *disable hardware acceleration in the Flash plugin<br>https://helpx.adobe.com/flash-player/kb/video-playback-issues.html *disable hardware acceleration in Firefox<br />https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration See also: *http://kb.mozillazine.org/Flash#Troubleshooting