W520 External monitor artifacts

[commander]

My W520 has a problem. On notebook only usage everything is OK. When I dock the machine and use external display via DVI port, I can see some sort of blinking/flickering artifacts. The worst is when displaying blue or gray gradients.

- I have optimus disabled, only using quadro 1000M
- using Legacy BIOS
- the problem is there both on lenovo install and fresh install
- GPU temps are fine due to HWmonitor
- tried both outputs on the dock
- cable is OK
- monitor is OK
- drivers are current

I am guessing a bad graphic memory. Do anybody seen this issue before? I put my machine into Lenovo shop a week ago but no updates and I am sad I cannot use my new thinkpad.

Here is a video of this problem (not from my machine) - you must watch carefuly
http://www.youtube.com/watch?v=g3XnqRK8K1k
Thanks