My friend has one of the last gen. 15 inch PB G4's and he called me with an issue he was having. He was prompted for an update and went forth with it. After the update was finished and the computer restarted, he tried to type in his password and it looked like it was logging in but it would go to the blue screen and then it would just go right back to the log in screen. I told him I had no idea what to do but I would post on here for him. Thanks.