Users are unable to authenticate at preboot after successfully installing DE, encrypting the hard disk, and restarting.

During startup, a blank black screen is displayed instead of the expected DE preboot authentication prompt.

This occurs on Toshiba Z50 models in UEFI mode when the Compatibility Support Module (CSM) option is also enabled. (CSM support is required when installing Windows 7 on the system when the BIOS is in UEFI mode.)