Every morning I log into Mac OS X by clicking my name in the login menu and typing my password. Today it would not take my usual password. It did the screen jiggle effect instead. Going back to the login list and clicking my name again did not help. I tried it a few times so I was sure I didn't misspell my password or have extra spaces before or after it. No other user was logged in. I had logged out normally after finishing with this Mac yesterday. I noticed a clue: There was an up-arrow in a circle on the right of the box where I type the password. I've never seen this symbol there before. Restarting the Mac cleared up the problem, so I am not stuck, but I don't like mysteries. What was that about?