Sorry if this is a double post but I just woke up and my MacBook greeted me with this, courtesy of System Update :- The SMC Update improves the MacBook's internal monitoring system and addresses issues with unexpected shutdowns. This update is recommended for all MacBook systems, including those that received warranty repair. The updater application will be installed in the /Applications/Utilities folder. Please follow the instructions in the updater application to complete the process. I think I'm just going to take the plunge now and I'll report back.