Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
Can FileVault 2 And Find My Mac foil thieves?
Apple has introduced a new way of tracking thieves by an excellent trick within the Mac OS X by combining the FileVault 2 with the Find My Mac Service of iCloud. FileVault 2 is an application used in Mac OS X Lion through which the Mac users can encrypt their entire boot drive. Any Mac operating system which have FileVault 2 installed in it and start or restarts, a login screen displays through which only the administrator of the system or an authorized user can pass out. All you have to do is to enter in the pass code assigned to each user after which the encrypted key will be unlocked and the system will start from the boot drive.
Behind the curtains, Apple has taken complete benefit of Recovery HD which is a partition in the startup drive and is invisible to the user. This partition has been made a part of the installation process within the Lion version and is used for both the situations whether emergency or regular activities. The application of FileVault has the mechanism of encrypting only a major portion of the Lion disk by making use of the unencrypted Recovery HD portion of the disk in order to handle the overall situation.
Additional Features With Lion 10.7.2
The release of Mac’s latest version 10.7.2 came out with new features within the FileVault application along with its nifty interactions with the latest feature of Find My Mac program. Among many, one of the changes made is the new option of Guest User which is displayed on the entry screen of the FileVault. This option will appear only when the users has booted up the system under the OS X 10.7.2 previously and had logged into the iCloud program.
After this the Guest User option is to be selected and the Mac will restart in a Lion Recovery Get Help Online mode. In case you have previously visited any of these networks, it will connect you automatically to that network. The basic difference both the modes is that the Guest User option of FileVault does not enables Apple menu’s Startup Disk option so as to select a separate drive. Moreover, the user cannot quit safari browser for opening other Lion recovery functions.
Now let’s determine what is actually going on behind the scenes. Under normal circumstances, Lion copies some of the configuration to the Recovery HD related to password validations, authorized accounts of FileVault as well as the passwords of Wi-Fi networks from which the user is connected and have selected to save the passcode. But, under OS X Lion, the Recovery HD also stores all the credentials of the user of the iCloud along with the enabled or disabled status of the Find My Mac application.
Combining all these elements, the whole scenario is that when any person uses the Mac system via the guest User option, the Mac gets connected to the Internet, logs into the iCloud invisibly, and traces your location through the Find My Mac feature. This is the crafty situation on behalf of Apple. If any user tends to steal out the FileVault enabled Mac system and boots it up, the user cannot gain access to any of the user account which will create temptation within them to boot from user accounts so as to gain access to the data or simply erase all the data from the drive. The time a user account is logged in, the location of the Mac operating system is revealed by making use of Find MY Mac feature.
There are some ways through which the protection can be enhanced. For beginners, when the FileVault if launched, it automatically requires a password and deactivates the option of automatic login. From this it can be derived, that not every person using your Mac can make use of this application which will likely make them to reboot the system and get their selves trapped into the User account trap laid down on the system.
Furthermore, it is also recommended to activate the Require an administrator Password to Access System preferences having Lock Icons. By this, any person who makes use of our unlocked Mac will not be able to configure the system level settings unless they are equipped with the valid administrator password.