Ever since Android 4.2.2 (a couple of days ago), rotating the Nexus 7 to portrait mode causes the screen to go black with a quiet “click”, usually within 10 seconds (the desktop is fine unless I perform an action, such as try to drag an icon). Once that happens, turning it back on causes an endless cycle of going black, a flash of whatever I was running at the time, then back to the lock screen. With the lock screen (security) turned off, the currently running App will come into view for a half second, then the screen goes black. Pressing the power button causes the App/black to happen again, if I keep it held in portrait mode. If I then position the tablet to landscape, I can sometimes get everything back to normal, but often have to shut down to get out of the cycle. I've tried a soft reset several times. It's fine when in landscape mode. The "Rotation Lock" setting doesn't seem to affect this issue, since most portrait games rotate to portrait mode regardless of that setting. I first noticed this when playing Pinball Arcade (then Zen Pinball and some dedicated portrait mode games), but it happens anytime it's moved to portrait. For Zen Pinball, I can make the tablet "sleep" by going to portrait, and have it wake by going to landscape, without pressing any buttons. If I'm very determined, I can get portrait to function as it should. I get into the loop, rotate to landscape drag an icon or whatever was causing Sleep, then rotate to portrait, and it's fine (no sleep). So once the tablet is 'finished its "rotate" process' and is staying "on" OK in portrait, it's OK -- for the currently running App. I'm running in ordinary Android, not rooted, no patches or anything, and tried killing all but 3 processes. This is the first serious bug I've seen in this tablet since I bought it a few months ago.