Lenovo Displayport to DVI adaptor - display not detected

[zern]

I bought a Displayport to DVI adaptor from Lenovo with my T420s.
Worked on the first day. External display detected and running.
Now the display is not detected anymore.

Is this supposed to be hot plug and play?

I have tried plugging in the display with the thinkpad on - no luck.
Put thinkpad to sleep with the display connected and powered on then reawaken - no luck.
Put thinkpad to hibernation with the display connected and powered on then reawaken - no luck.
Rebooted thinkpad with the display connected and powered on - no luck.
No detected by the WIndows 7 control panel, or the Intel tool, or the Nvidia tool.

VGA works instantly.
Have tried a different monitor (different manufacturer). Still no luck.
Direct connections - no docks involved.
I don't have any Displayport devices here to check if my Displayport is the problem. Hope not.
All Windows and Lenovo drivers are up to date.

Any thoughts?

[chairsky]

Is this supposed to be hot plug and play?
---------------------------
Unfortunately NO.

[zern]

Hmmm. Not plug and play could shed like on this. Maybe it didn't like the cable being removed without first disabling the external display? (The cable was removed when the unit was in hibernation, not powered up - but the external display was not disabled in Windows).

Weirder and weirder The external display is not detected once more. I left the cable plugging in (display undetected) over a few hours of the thinkpad in hibernation. When I came back the display powered up.

Fingers crossed this is just part of the getting-used-to-the-new-quirks process of a new machine.

Thanks for that thought. I will disable the external display before yanking the cable in future.