This week is full of...updates! Apple has issued a small update to the firmware for their 2009 Aluminum Keyboards. The update follows the recently released one for their 2007 model keyboards, and should not be confused with it. If you tried updating your keyboard with the old update and failed, it is probably because you have the newer keyboard model.
This update addresses the same issues as the version 1.1 update for the 2007 model keyboard, which is the battery performance of the keyboard when used in combination with other Bluetooth devices.
The update should be available through Software Update but also is available as a standalone update at Apple's Web site: http://support.apple.com/kb/DL1003
As with other firmware updates, this will put an updater application in the utilities folder that will be launched automatically to provide further instructions. You will need to ensure your computer is plugged in to a power supply, and be sure your keyboard is on and paired for the update to work.
Specific instructions for the update can be found here: http://support.apple.com/kb/HT4019