Hi Silvercue,

  I think you got it.

After reading your post, i closed my Nexus cover, and lo..it does automatically blanks out and returns when i open it.  i am using it right now for 30mins, with cover unfolded,with no black out.

I wonder why, considering my cover is all leather, with hard plastic as backing.

I am already thinking of resetting it. Anyway, Will observe for the next few days.

I'm really happy. Thank you very much.

Similar problem as Merino's. My Nexus suddenly turns off and/or screen suddenly blacks out, regardless of what im doing. During log in, it blacks out again. I have to push the power button and retry log in before it  finally works again. My Nexus is 2 weeks old. Would appreciate help. Thanks.