Apple has released new firmware software for MacBooks that should address the widely reported intermittent shutdown problem affecting many units.

MacBook SMC Firmware Update 1.1 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," Apple stressed.

Users need to have Mac OS X 10.4.7 or later in order to install the update, which must not be interrupted once it is begun.

The company has claimed the firmware update will repair the intermittent shutdown problem, which is caused by some heatsinks inaccurately gauging the Mac's running temperature, moving to shut the Mac down in order to protect it.

Apple has been replacing the component in affected Macs up to now.