Problem 

Some DELL Latitude systems can fail to boot after they have been Full Disk Encrypted.

The problem is exhibited by a black screen with a flashing cursor at boot time. This can occur directly after the system is Full Disk Encrypted, but can also occur at a later date after numerous successful reboots.

Systems known to be affected

The following DELL Latitude systems are known to be affected when Legacy BIOS is enabled and SATA Operation set to either AHCI or RAID On. Systems booting in UEFI mode are not known to be affected.

• E7250
• E7350
• E7450 (7000 Series Ultrabook)
• E5250
• E5350
• E5450
• E5550 (5000 Series Laptop)

Cause

Certain versions of the BIOS in these DELL Latitude systems are known to have a bug, which causes software Full Disk Encryption to be unable to access the disk correctly during boot. This not only affects DESlock+ Full Disk Encrytion, but many other manufactures of software disk encryption. 

Solution

DELL have provided a BIOS update that fixes the problem. This is available here : http://www.dell.com/support/article/al/en/aldhs1/SLN296627 

Please note: You may need to boot the system to Windows to apply the BIOS update. In this situation it is recommended to install Windows on a second disk, which can be booted from and the BIOS update applied. Once the BIOS is updated, return the original disk to the system.

After updating the BIOS, the system may still not boot

If after updating the BIOS the system does not boot, it is possible that the original problem BIOS had blocked access to the systems Master Boot Record (MBR).

The DESlock+ MBR must be restored. This can be done using the DESlock+ Recovery Tool.

Please see http://support.deslock.com/KB222 for details.

keywords: dell preboot laptop latitude  E7000 E5000