I've had this G5 for well over a year but after Leopard was installed a month ago(December) it has, on occasion sounded like it was going to explode. I've never heard the fans this loud and i'm sure the hard drive is also going at high speed. Is there any way to fix this "problem"? Incidentally, the screen also goes black and there's no way to prompt the system without just shutting it down and restarting. Thanks in advance.