I have a clean install of OSX 10.5. The system will 9 out of 10 times, not shut down after I go to the apple and choose shut down. It closes all apps and the spinning lines appear (not the colored rainbow spinning wheel), but that is where it stays until I press and hold the power button. I do run with external USB drives almost daily, but it doesn't seem to matter that they are plugged in or not. I do have Bootcamp right now, but this problem began before I put Bootcamp on. Any ideas?