You cannot start a Windows Vista-based computer by using a BitLocker key that is stored on a USB device

After you configure BitLocker Drive Encryption to use a key that is stored on a USB device, you cannot start a Microsoft Windows Vista-based computer, even though the USB device is connected.

This problem may occur if the computer's BIOS cannot read the data on the USB device when the computer starts.

To resolve this problem, use one or more of the following methods:

• Make sure that the USB device is connected to one of the computer's USB ports. For example, do not connect the USB device to an external USB hub.
• Store the BitLocker key on a different USB device. The original USB device may not be compatible with BitLocker.
• Disconnect other USB devices from the computer. The computer's BIOS may not able to read the data on the USB device if other USB devices are present.
  
  Note The order in which the BIOS detects USB devices may affect BitLocker.
• Contact the manufacturer of your computer or your motherboard to make sure that the computer's BIOS can read data from a USB device when the computer starts. You may be able to update the computer's BIOS to a newer version that supports BitLocker.
• USB Devices that are used to start Windows PE or other operating systems may not work with BitLocker. Reformat the USB device so that it is not used as a startup device.

When this problem occurs, you may be able to start the computer by entering the recovery password.