The fastest way clear it, would probably be restarting your device (I assume PC in this case). After the restart, you should be able to remove it without any issues. If you want to avoid the restart you can try following: 1. Open task manager and select details tab. 2. Look for any Firefox related processes. If you find any, terminate them. 3. If you can't find them there, look at services tab. Search for Mozilla-related services and stop them.

Hopefully, this helps to solve your issue. Good luck!

Thanks. Immediately on booting up there was the same situation. Task manager said no apps running. Clicking on 'detail' and scrolling down, I found the little Firefox blighter. Closed it, and was then able to uninstall.

Thanks for your help.