I just returned from an out of town mini vacation attending a painting seminar. The event was in Garland, TX which is a 5 hour drive from my home in Austin, TX. It was really hot yesterday, close to 100 degrees and I made a couple of stops which not only extended my drive time, but meant my car was hot during those stops. And, I made a mistake — I forgot to shut down my Mac before I started for home.
When I got home, unpacked, and tried to read my email, Mail would not let me in the program unless I entered my administrative password. When I tried to do that the computer took over and entered element after element. For instance, if my password were 123456 and I tried to enter that, the computer would continue to enter something and I would have no control over it. I had to go to the Apple Menu > Force Quit to get out of Mail and end the action. I tried to open Safari and had the same results so I knew the problem had nothing to do with Mail and everything to do with my OS. A shut down and restart did not solve the problem.
So, I banged my head against the wall for being so stupid as to fail to shut down before leaving for home – a step I recommend you skip – and opened disk utility to see if that would help.
Disk Utility is in your Applications Folder > Utilities, but the fastest way to open it is to enter utilities in Spotlight. It will probably be the first thing on the list and you can just click on it.
When this window opened I selected my hard drive, clicked on Repair Permissions, and let it do its thing.
When it finished, I restarted my computer (not required, but a good idea), and everything was back in good working order.