I got my 2 GB memory upgrade from DMS today, and proceed to install them. But now my MacBook wouldn't turn on. All I get is the power indicator light flashing. What does this mean? I can't find it anywhere in the manual or the support site on Apple.com. What does that flashing light mean? I've tried removing the RAM and putting back in the previous 512 MB stick, and got the same problem. What do I do?