I update OS X whenever Apple pushes the notifications. I have a macbook and imac bought in August 2011. Last week the password on my macbook wouldn't work. I hadn't done anything to change it or noticed anything unusual before. **** happens, I reasoned and changed the password in terminal. This week the same thing happened on the iMac! I only a browser on the macbook. I don't use a browser or email on the imac. I don't visit spurious sites or download software except from trusted application sites. I try to keep up on what's going on in the industry, but is there a virus making the rounds I've not heard of? A password changing on one mac is very unusual, but two is very unlikely. Any thoughts?