Sounds like you have the same (or very similar) for your Buffalo hard drive that I do. I have two of the Buffalo Ministation HD-PZ1.0U3B, which is a 1 T hardware-encrypted drive. Yes, red light when encrypted then green after the password when on a USB
3 port (or blue light if you plug into a USB 2 port). I have been unable to get the drives of this type to work with the Surface Pro 3 even though they work on all other PCs I have (DELL laptop, DELL workstations, even a Macbook Pro Bootcamp partition).
I don't have access to another Windows 8.1 machine, so can't say for sure it's the SP3 and not Windows 8.1, but I think it isprobably due to the tricky SP3 power management.
Symptoms: the virtual CD comes up, then I can log in and then I can access the mounted drive, BUT it drops out (red light comes back on, then eventually that goes out too) if I do not access the drive at least every 30seconds. I was able
to get it to stay up for 1/2 hr by having TeraCopy move over 29 G of files. But once you stop accessing it, it drops out after 30s and Windows Explorer doesn't even realize the drive is not accessible -- if I try doubleclicking a file name in the list at
that point, I get a long hour glass, a fade-out, and then I/O errors reported in the Event Viewer.
Buffalo support says it's Microsoft's fault. Microsoft support says maybe the drive is drawing too much power. I think Buffalo is right, since I measured the current (220 mA, far less than the 500 mA that even USB 2 can supply) and in
fact the drives act the same way whether run from the SP3's USB3 port or from ANY of the ports on the SP3 dock which I usually have it plugged into. The dock is rated at 48 watts!
My drives give up the VCD drive letter to the decrypted drive when it mounts. Maybe that has something to do with shutting down after 30s idle, not sure. Microsoft issued a patch (firmware, I think) not long ago to fix many of the USB device start/stop/disconnect
problems, but I still have issues with the Buffalo after I put in all the updates. My other portable drives and USB sticks work just fine (but they are not hardware encrypted). I've searched forums to no avail -- I did find a few others with different hardware
that mention a 30s to 35s idle time before being dropped.
It's a mystery -- I might resort to registry edits. Some people claim this fixed their problems: http://blogs.msdn.com/b/usbcoreblog/archive/2013/11/01/help-after-installing-windows-8-1-my-usb-drive-disappears-or-file-transfers-stop-unexpectedly-r-a-post-title.aspx
. That might force off the power management (just in case clearing the power management check boxes in Device Manager aren't doing the job correctly). Gotta back up the registry and my hard drive first...