[nsa_sailor]

I searched the registry and found
HKCU\ControlPanel\Keybd\DeviceLockWhenSuspend
HKCU\ControlPanel\Backlight\AutoDeviceLockTimeout
HKCU\ControlPanel\Backlight\AutoDeviceLockEnable

I think I disabled the AutoDeviceLockEnable and that made the phone quit locking, but I look now (after I had done a hard reset) and that value is set to 0 and the phone still locks when the backlight goes off. You might change it to 1 and see.

I know I changed one of these keys (but I don't remember which one) when I had messed up the slide to unlock feature and had a blue screen unlock.