Apple’s patch notes:
- Resolves an issue that sometimes caused high processor utilization while playing audio through the headphone output mini-jack.
- Resolves an issue that prevented the display backlight from turning on after powering on the iMac.
The update is a 2.1MB download through Software Update (if you have a 27” iMac). It requires Mac OS X 10.6.3. Follow the on-screen instructions for installing the update.