The rubber things that connect the screen to the rest of the tama, as sailor rosette mentioned, might be loose. If you accidently drop one or both of them , actually, it dosen't matter, you can just put them in place again and the tama will work.
One of my friends happened to drop one, and instead of just putting it back, she glued it on, and as a result half of the screen died completely. We managed to wash most of the glue away, and it worked again, except for one pixel row in the middle.
Even id the rubber thingys are in place and all, it might be good to just open it up anyway. I usually open upo mine when they act weird, just to see that everything is in place
.
Maybe a switch of battery could fix it, even though I doubt that.
