W540 + Dock + Dual U28D590 (UHD) monitors

Question

Hi,
I have a W540 dock previously driving 2xDell U3011 monitors. It worked okay (there were problems with the U3011 going into a sleep-freeze-hell mode but from what I could gather it was more a problem with the U3011 firmware).
I've just upgraded (or tried to) to 2xSamsung U28D590 UHD monitors. This does not appear to work well at all. I've experienced the following symptoms in the following conditions:
(excuse bullet point formatting - cannot figure out how to nest bullet points)
One monitor plugged in - either monitor, on either display port - works fine. Monitor goes to native, laptop lcd goes to native.
Both monitors plugged in, Laptop open - I can drive ONE of the D590's to the native (3840x2160) resolution. The other monitor connects at 1024x768. Any attempt to change resolution on this one gives the ambiguous "Unable to save display settings" error.
   Any attempt to disconnect the laptop screen in the screen configuration also gives the "Unable to save display settings" error.
Both monitors plugged in, laptop closed
   Ths initial state here is glitchy. The screen config thinks both screens are on, but only one is actually showing anything. It is also periodically flickering (the screen goes dark, for maybe a tenth of a second) as if it is in a lower-power configuration, and as far as I can tell this is happening consistently at 1hz. I haven't run this for long because I am afraid it is doing damage to the monitor.
   After some tinkering I can get both screens to show at 2560x1440. Any attempt to push either screen to native simply causes the screen to flicker and the "Do you want to keep these display settings?" prompt to come up - however the screens remain at 2560x1440. 
Has anybody else had any experience with trying to drive 2 UHD monitors? I'm really hoping I haven't just wasted a lot of money.
I'm happy to not use the laptop LCD if that is necessary. I would try discrete only BIOS mode but this has been removed for reasons beyond my understanding.
My configuration:
Windows 7 Ultimate x64 SP1
W540
   - 20BGCTO1WW.
   - Bios version GNET60WW (2.08). I know the BIOS is old - the laptop originally shipped with 2.09 - but I had all manner of hellish problems getting my RAM to work (see http://forums.lenovo.com/t5/W-Series-ThinkPad-Laptops/W540-with-G-Skill-F3-1866C10D-16GRSL/td-p/1459... and ended up downgrading. I've checked the BIOS changelog and nothing seems to relate to this issue so I have avoided upgrading for the moment to avoid the risk of bricking my laptop
   - 2880x1620 LCD
   - Quadro K2100M - drivers 9.18.13.1269
   - Intel HD Graphics drivers 10.18.10.3910
Dock 40A20135AU (yes, the 135W dock - I was told on these forums this was okay, and indeed is the unit shipped/recommended for the W540 by Lenovo Australia).
   - I believe I've upgraded the firmware available from here http://support.lenovo.com/us/en/documents/pd028011 . I'm not 100% because after running it, it showed a progress box for flashing which disappeared and there was no confirmation prompt.

Answer 1

Colonel, just realised I didn't answer your previous question - yes, I am driving both monitors from display port cables.
I've updated the NVIDIA Drivers to 9.18.13.1269. Unfortunately this hasn't made a difference (well, it has broken wake from sleep again, but it has not helped)
I've also installed the monitor drivers but this also has not made a difference unfortunately.
ptdh thanks for the information. The fact that I was able to drive a single monitor at 3840x2160 makes me suspect something else is afoot. Not entirely sure if the Pro2840m drivers would work at all on my monitor or even a good idea - from what I understand they are different panels?
Maybe there's just better inherent support in Win8 because of the drive for retina level everything. At the moment unfortunately I don't have time to go and install Win8 on a test drive just to check this.
I have a suspicion it might be a problem more with the Intel side of things thanks to the convoluted optimus display. But sadly I cannot force discrete at a low level because in their infinite wisdom Lenovo have removed that option from the BIOS.
Also tried installing the Intel drivers (not sure if the correct ones - here https://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=23764&lang=eng&ProdId=3319) but unfortunately due to the usual OEM/Vendor faffery they won't install on my system. 
If anyone else has more input (any official comment from Lenovo rep? I have emailed support but it's been radio silence so far)