Samsung Galaxy Tab 2 P5110 freeze. Can not turn it off

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http://forum.xda-developers.com – Hi, yesterday I rooted my Samsung Galaxy Tab 2 P5110 and flashed CM 10.1 RC2. First I worked like but then it freezes and just leaves a black screen. If I press the power button for about 10 seconds the backlight goes on for a couple of seconds and then again a black screen. It seems that the tablet is frozen. If I connect it to my PC it will be mounted as "GT-5110" and I have access to the intern and extern sd-card. If I ping the ip address I get a response. But I can not turn it off! Tried a lot of power, power+louder, power+silencs button combinations. Any ideas wha (HowTos)