This morning I booted up my mac like any other morning, but this morning it just loaded up with a white/grey screen and stayed there. No Apple logo whatsoever. So ok, I thought restarting it would do, no. So i unplugged anything into the mac apart from the keyboard and mouse. Booted it up and it worked, loaded up Leopard. Now should I be worried about this? If it happens again when I boot up tonight?