Get message, "Could not initialize the application's security component. The most likely cause is problems with files in your application's profile directory. Please check that this directory has no read/write restrictions and your hard disk is not full or close to full. It is recommended that you exit the application and fix the problem. If you continue to use this session, you might see incorrect application behaviour when accessing security features."

Tried again, and it downloadeded but hung in installation while "checking comp-atibility of add-ins." I canceled out, but FF10 loaded anyway, but was inopperable. Closed it and then restarted. FF10 loaded, but was still inopperable.