Hi, a few things to try - See if it runs if you temporarily disable your security program. If it does, see if their is an update and look at the settings for anything which might hook into browsers. --------------------- Hold down the Shift key when you start Firefox to start in Safe Mode. More - [[Troubleshoot Firefox issues using Safe Mode]]. If it works in Safe Mode, disable any theme or add-ons you have - Add-ons Manager (Ctrl+Shift+A) > Themes/Extensions and restart Firefox; then if it's OK, re-enable them one by one until you find the culprit. You may need to restart Firefox after enabling some add-ons. ------------------------------- Download Firefox from https://www.mozilla.org/en-US/firefox/all/ ------------------------------- Try a Clean Reinstall; this means you remove your Firefox program files and then reinstall Firefox. This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location. With Firefox closed, use another browser to download Firefox from https://www.mozilla.org/en-US/firefox/all/ and save the file to somewhere convenient on your computer. Now delete the Firefox installation folder which should be in one of the following locations - C:\Program Files\Mozilla Firefox C:\Program Files (x86)\Mozilla Firefox You can now double click the file you previously downloaded to install Firefox. ''If your question is resolved by this or another answer, please take a minute to let us know. Thank you!''

Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems. *http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/ *http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10