I tested with OS2008 for N810 which I have installed on my N800.

The screen went black (2 minutes to dim, 5 minutes to blackness with 5 minutes set for autolock) at which point I tapped the screen and up popped the number pad asking me to enter the unlock code.

It could be a one off glitch in your OS 2008 Beta installation, but for me it's working the N810 OS on N800. Someone with OS 2008 Beta must be able to confirm if it's working or not!