If the computer freeze when moving it and you get lines and artifacts in the screen then the GPU (graphic processor unit) could be the culprit. Connect the PB to an external monitor and check if the video signal is normal. If not, prepare yourself for a logic board swap. If the video is OK on the external then the problem could be a bad LVDS cable but a bad video cable would not be the cause of the computer crashing. That's why I think the graphic card is faulty.