Ed, with some electronic devices I own, and my 17" PB is one of them, it just stops working as designed. Restarts do not fix. But a shutdown, and sometimes removal of all power (AC and battery) for a period of time (probably minutes is all that is needed, but I usually give it hours) allow the wayward electrons to drain away, chips settle down, and internal harmony returns. This happens more frequently with my satellite TV box, but it happens. I visualize the problem as the "electrons have lost their way and do not know how to find home." I do not think it is related to the temperature of the mac overall, or even a specific component. I just think that the machine has become so complicated, it sometimes loses it way. Anyway, that is my story and I am sticking with it. Lee On Mar 20, 2009, at 1951, Ed Gould wrote: I tried booting my system and all I got was the APPLE screen and a forever turning circle (or whatever it is called). This happened 4 or 5 times....