I just bought 2 nexus 7 tablets for my sons. One has updated to jelly bean just fine, but the other downloaded the update than rebooted than the android fellow came up with the thing spinning in his stomach, than he fell down with a red explanation mark in his stomach. What does this mean? I'm back and running but jelly bean has not been installed. Thinking I may take it back and just get another one. I already did a factory reset but it did the same thing. Any suggestions?