Suddenly my MacBook Air won't accept my password. When I restart, the first screen offers to let me login with my username and symbol, and accepts my password, but then opens a screen giving me the option to logon as Guest or a fill in the blank Name, and if I put on my name and password it doesn't work. I can't get past this except as guest so can't get in the Apple menu. Any idea what is going on and what I can do ? Have tried restarting, turning off, logging in as guest, and still locked out.