Consider the following scenario. In Windows Vista, you configure Microsoft BitLocker Drive Encryption to use a key that is stored on a USB device. You then disconnect the USB device when the computer is in hibernation. In this scenario, you may receive the following error message when the computer resumes from hibernation:

BitLocker Drive Encryption key needed.
Please insert key storage media.
Then press ESC to reboot.

When you receive this error message, you must restart the computer.