I'm not sure if it came up while you were posting your question, but there are several troubleshooting suggestions in this article: [[Firefox won't start - find solutions]]. ---- Could you try starting Firefox in its Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: [[Troubleshoot Firefox issues using Safe Mode]]. Hold down the Shift key when starting Firefox. A small dialog should appear. Click "Start in Safe Mode" (''not'' Reset). Will Firefox start up? ---- Sometimes a strict "program control" firewall or malware will stop Firefox from running. You can investigate these possibilities further using the steps/tools in these articles: * [[Configure firewalls so that Firefox can access the Internet]] * [[Troubleshoot Firefox issues caused by malware]]