Firefox was working fine until two days ago. I've made no major changes to my system in that time. The program now opens normally several times, and then crashes upon start-up. After several attempts to reopen it will prompt me to enter it in safe mode. It then works. However, it's only a temporary fix. After using it a few times without incident the problem begins anew with no apparent cause. There's no obvious pattern to the crashes. I've tried all the recommended fixes: updating Firefox & add-ons, disabling all add-ons and extensions, virus and malware scans and resetting Firefox. (I use the standard theme.) I even uninstalled and reinstalled the program. Nothing helps.