A few people who have purchased retail copies of the latest iLife '11 suite from Apple have complained that the installer will not work. When installing using the DVD, the installer may hang halfway through its progress, or stop with an error stating that the manufacturer (Apple) should be contacted.
A number of people are finding that this appears to be from the media the software is being distributed on. There may be a problem with the drives being able to read certain sectors of the media, at least for a standard installation of the drive.
If you are affected by this problem, there are several approaches you can take:
Image the DVD
Though the DVD may be failing to read during installation, you might have success by creating an image of the installation disc and installing from there. To do this, open Disk Utility and select the iLife installation disc in the list of devices. Then choose the "Disk Image From devicename" option in the "New" submenu of the "File" menu, optionally choose a desired image format ("compressed" may take a little longer to create but will be a smaller file). Save the image and if it completes properly, open it to mount it and try installing iLife from there.
Reburn the DVD
If you get problems with creating the image on your computer, the problem may be with your drive's ability to read that disc, and another drive might be successful. Try creating the image on another OS X system and either copy it to your current computer to mount directly, or try reburning it to another blank DVD using Disk Utility. While burning has been greatly perfected over the years, one way to reduce the probability of burning errors is to reduce the burn speed for the disc.
Besides Disk Utility, you can also try a third-party burning utility like Roxio Toast Titanium, which uses a separate reading and verification routine than Disk Utility, and may give better results when imaging or burning the DVD.
Replace the DVD
The last option is to contact Apple about the issue and have the company replace the iLife DVD. If you are near an Apple store, you can likely bring the disc in and have someone swap it out for you right there.