I have installed Ubuntu 12.04 LTS on my HP Elitebook 2540p. I have installed on a 64GB SDCard. (It has been quite a journey to make it boot from the SD-Card but now it works :) )
My problem is that, after resume, I do not get the unlock prompt. I do get the normal background and the mouse cursor is there and operational the dimming and display turn-off and on works normally. -Only problem is that I do not get any unlock prompt.
If the system is locked by timeout without suspend, the unlock prompt appear as expected.
Also, when running from a USB-Stick or from an external Hard disk. This problem does not appear. Further I have tried Ubuntu 12.10 as well as 13 with exactly the same behavior.
I should mention that I have reinstalled several times and this problem is really predictable.
It seems like the SD-card somehow triggers this problem.
Any suggestion where to start looking for the cause?