UEFI problems:  I have found that Bitlocker will not be able to use the enhanced PIN as specified in our GPO on the Thinkpad T420 when using UEFI.  The problem lies in the BIOS (yes, it is still called the BIOS, even though it is UFEI) and it requires an updated version so that the keyboard keys are represented properly (alpha characters) during the boot phase of the startup. My T420 had version 1.24 of the BIOS, and version 1.25 seems to fix this issue. Here is a snippet of the Release Notes for 1.25: [more]

CHANGES IN THIS RELEASE

  Version 1.25

[Important updates]

  Nothing.

[New functions or enhancements]

- Added support for the Password Beep function.

- Increased the number of configurable boot devices by BootOrder option of

  Windows WMI script.

[Problem fixes]

- Fixed an issue where the BitLocker function could not be enabled on Windows

  64-bit.

- Fixed an issue where PXE boot might fail.

- Fixed an issue where the fingerprint authentication associated with some

  password strings might fail.

- Fixed an issue where the Intel TXT feature might not be enabled when the

  Security Chip was activated and the Intel TXT feature was enabled at the same

  time by ThinkPad BIOS Settings Windows program.

- Fixed an issue where the Bluetooth wireless status indicator might be changed

  after running Windows WMI script.