help! my macbook is doing something new and strange yet again. when i turn my computer on it brings me to the login screen but instead of my picture there is a pcture of a silloute with a question mark inside. instead of my name it says '[update needed]'. when i put my password in it shows the apple logo the goes right back to the login screen and imediately freezes. it wont bot into safe mode and holding the option button reults in a picture of my hard drive with no other options. someone please help me im wracking my brain!