I bought a Google Nexus in China. Since China does not officially sell Nexii, it is contraband. But I had no other options for a pentaband phone on extremely short notice. It is, however, a real Nexus. Not a copy. I bought a China Unicom card. The Nexus functions happily without a SIM card, but when I put in the SIM card, reboot the phone, 5 seconds after booting up the screen will just shut off. The power button doesn't respond. Nothing responds. I have to take out the battery. The card DOES work. I was able to connect to Google on the card once before it "shut down." I'm at a loss as to WTF is going on. How does a SIM card make this happen? The OS is completely stock 4.1.2, unlocked.