My Macbook Air is exhibiting a number of symptoms consistent with the need to reset the SMC (keyboard backlight erratic, shutting down when closing the lid instead of sleeping). However, I have another problem which seems to render the SMC reset process useless... I am unable to startup my MB with the power cable attached. It will only boot once it is unplugged and running on battery. The SMC reset process requires the laptop to be plugged in whilst holding down the Shirt-Control-Option & Power buttons. I've tried the process both plugged in and unplugged and neither has any effect. My laptop still shuts down when I close the lid. Pain in the proverbial. Anyone have any ideas? Thanks in advance for any help. Michael.