In addition to the iLife update, Apple also updated the iDVD authoring software. iDVD 7.0.3 "improves overall stability and addresses a number of other minor issues."
Both of these updates are available to iLife '08 users. You can update using Software Update (Apple menu > Software Update) or by downloading the two installer packages from Apple's Support Downloads site. Note that these updates do not affect the newly released iLife '09.
Thanks to Tarun for the tip!