Windows – Bitlocker won’t initialize on a 4TB drive with 4K sectors

I'm trying to enable BitLocker on a 4TB drive with 4K physical sectors (Advanced Format) on a 64-bit Windows 7 box with SP1.

The drive is partitioned GPT (1 partition using all of the available space) and formatted with NTFS.

When I right click on the drive and select 'Turn on BitLocker…', a dialog appears that says 'Staring BitLocker' and 'Please wait while BitLocker initializes the drive'. There is also a warning (same dialog) that says 'A device attached to the system is not functioning.' The progress bar never moves and there is no disk or CPU activity. I'm not seeing anything in the event viewer, either.

How do I get BitLocker turned on for this drive?

The drive is is a 4TB Hitachi DeskStar 7K4000 in an internal bay connected via SATA-II (host has no SATA-III ports). It's not a boot drive. I'm creating a single GPT partition (using the whole drive). The motherboard has an Intel P55 chipset with no TPM. No yellow exclamation marks in Device Manager. I've waited over an an hour, nothing happens with the dialog box. The drive has 4K physical sectors, 512 byte logical sectors (it's Advanced Format 512e/512 emulation, not 4Kn/4K Native).

When I formatted the volume, I left the allocation unit size at 'Default', which ended up being 4k. Is there some requirement for a different allocation unit size for volumes over a certain threshold size?

It seems that I can create a smaller partition (2TB) and there is no problem. It seems that the magic limit is 3815174 MB, which is a 144 MB less than the available capacity of 3815318 (according to the New Simple Volume Wizard). Can anybody explain that? I updated the motherboard BIOS to the latest version, that seems to have had no effect on this issue.

I want to know why I Bitlocker fails to encrypt a single partition using all of the available space (according to the 'New Simple Volume Wizard), but will encrypt a partition 144 MB smaller? I have 2TB Hitachi drives with a single partition, no unallocated space and they encrypted just fine. According to the Disk Management snap-in in the Microsoft Management Console, I have 145 MB of unallocated space on the 4TB Hitachi. A way to avoid wasting the 145 MB would be nice. It's not a lot of space, but I don't want to screw around with finding the magic number again on a different 4TB drive.

I just tried to encrypt a 3815318 MB single volume on the drive with the manage-bde command line tool:

manage-bde -on X: -RecoveryPassword

I get this:

Volume X: [New Volume]
[Data Volume]
Key Protectors Added:

ERROR: An error occurred (code 0X8007001f):
A device attached to the system is not functioning.