I have a Unibody Alu macbook...been taking great care of it since I got it over the last 4-5 months.. It was in sleep mode and I just opened the lid and I got the rainbow circle thing..and my macbook was ticking..I closed the lid and opened it and nothing happened...I rebooted and my hardisk ticked again and I got the boot screen with a question mark. I switched it off, took out the battery and rebooted it and I'm back on it now..and it seems normal.. What happened? What should I do? Thanks..