My Mac Pro, running Snow Leopard 10.6.8, keeps crashing with a gradient gray bar starting at the top and moving to the bottom of the screen and then a black box appears in the middle of the screen telling me I have to reboot. I have attached a jpg showing the error messages and I hope someone can decipher the error reporting message and what they mean and if that is my problem. Hopefully someone can decipher the code and can help me. Thanks.