I take it I'm the only one this is happening to?  I can't believe everyone would just accept this behaviour.

Or perhaps no-one else uses this monitor in conjunction with other monitors (2 x 2007WFP).

Would a video help to demonstrate?

Ok, this is what I mean...

Radeon HD 7990 --> 2007FP (What cabling? To what port on the Radeon HD 7990?)
Radeon HD 7990 --> 2007FP (2) (What cabling? To what port on the Radeon HD 7990?)
Radeon HD 7990 --> UP3214Q (What cabling? To what port on the Radeon HD 7990?)

It appears that when all three are on, the UP3214Q is the primary and the others are in extended mode. As a test, make the left 2007FP the primary and the UP3214Q and 2007FP (2) extended. Then turn the UP3214Q off. Does it still drop from the Device Manager? Does the 2007FP (2) drop from the Device Manager if you turn it off?

Thanks for responding.

If I make the left 2007FP primary, I still get the same effect.  Neither 2007FP drop from Device Manager when turned off, regardless of which way I configure the displays.

Connections on the 7990 are as follows:

DVI -> unused
mini-DP #1 -> DP on UP3214Q (using cable supplied with monitor)
mini-DP #2 -> passive DVI adapter -> Left 2007WP
mini-DP #3 -> active DVI adapter -> Right 2007WP
mini-DP #4 -> unused

For my notes, what operating system are you running? Is the USB 3.0 Upstream cable connected from the UP3214Q to the computer USB port? Until we can replicate this in the lab, I would not turn the UP3214Q off via the power button. Instead, set the operating system power management to turn the monitors off after X minutes.

I'm running Windows 7 Ultimate 64 SP1.  The USB 3 cable is connected to a USB 3 port on the PC.

I'll just use the O/S power management for now.

Thanks.

Did you manage to get anywhere reproducing this issue in the lab?  

I've also tried swapping around which mDP connection I use on the graphics card, but it has the same effect.

Ok, thanks for the response.