A possible cause of the problem: I've noticed that after locking the device, if the screen is still on and I press one of the two keys on the left, the message "Move ... to unlock" appears and the screen remains on. So, if one of these keys was pressed when I put the N810 in my pocket, the screen could remain on for quite a long time. This could explain why the problem occurs infrequently (for me). Now, I didn't have any such problem with chinook. Has anything like that changed between chinook and diablo?