I have frequently found that when Firefox is ready to update to a new version, it will quit working. More precisely, if I do not update to the latest version when prompted, and then I close the application, the application will not start when I go to use it again. No error messages are provided...the application will simply not open. If I want to get out onto the internet, my hand is then forced to use another web browser (i.e. Safari) to download the most current version of Firefox, install it, and then Firefox will once again open with full functionality. This problem is frequent...I find that it occurs each time Firefox has a new update ready, and it has happened on every Mac Os edition since the original OS X. Please let me know, if possible, why this is occurring.