this is my first mac, i installed the 10.6.4 update the other day and restarted, since then it has been on or sleeping. I just shut it down and turned it on again and it's asking for my password... each time i enter it goes to load and then comes back to the log in screen. I know I have the write password because it's a simple 4 digit one that I use for my bank account and if i enter anything else the box shakes and asks me to re-enter it. how do I log in?? am i missing something completely obvious?