I am now having this same problem. If I detach the screen, it does not auto-rotate. Something is weird, because the detach function now operates strangely. Usually, I push the button, the green key light comes on, the green sign pops up, and I hear the click. Now, the red key light comes on (wrong light), the green sign does not pop up, and after a while I hear the click. The auto-rotate sign pops up, but the screen does not auto-rotate and the tablet is stuck in landscape mode. Detaching and reattaching has no effect.
I seem to be able to fix it with a reboot, but having to maybe reboot every other time I want to detach the screen is becoming a pain in the butt. It does not seem to happen after waking from sleep - only after waking from hibernate.
The tablet that can replace your laptop (unless you actually want to ... you know ... use it as a tablet).