I've just bought MacBook with pre installed MacOS 10.6.1, then updated it to 10.6.2. Sometimes (approximately 1 of 5 times) it does not shutdown - there are only my wallpaper and active mouse pointer. I've been waiting for a long time, then just turned off it with holding power button. It seems I have a problem after high hard drive activity (a lot of copy, delete and move operation), but I am not sure. Could you help me, please?