It seems that under some unknown circumstances you will hose your iLife 8 installation so that Garageband, iPhoto, etc and other applications which depend on iLife like Mail.app, iChat.app, Google Notifier, Pages, etc will not lauch.

Mine probably stopped working after I installed Garageband from my Macbook's bundled software DVD, which I had not initially installed.
Symptoms: The app will bounce few times in the dock, close and you will get the following crash report (Example Crash Report for iPhoto, it's the same for all other apps):

Process:         iPhoto [413]
Path:            /Applications/iPhoto.app/Contents/MacOS/iPhoto
Identifier:      com.apple.iPhoto
Version:         
Build Info:      iPhotoProject-3640000~10
Code Type:       X86 (Native)
Parent Process:  launchd [177]

Date/Time:       2008-05-04 16:14:58.097 +0800
OS Version:      Mac OS X 10.5.2 (9C7010)
Report Version:  6

Exception Type:  EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000002, 0x0000000000000000
Crashed Thread:  0

Dyld Error Message:
  Library not loaded: /System/Library/PrivateFrameworks/GraphicsAppSupport.framework/Versions/A/Frameworks/ImageKit.framework/Versions/A/ImageKit
  Referenced from: /System/Library/PrivateFrameworks/iLifeMediaBrowser.framework/Versions/A/iLifeMediaBrowser
  Reason: image not found

Checkig the directory will possibly confirm, that the A directory in /System/Library/PrivateFrameworks/GraphicsAppSupport.framework/Versions/A/Frameworks/ImageKit.framework/Versions/ is not there:

$ ls -l /System/Library/PrivateFrameworks/GraphicsAppSupport.framework/Versions/A/Frameworks/ImageKit.framework/Versions/
total 8
lrwxr-xr-x  1 root  wheel  1 Apr 30 22:11 Current -> A

Howto fix this:

1. Cry like a baby.
2. Don't panic!
3. You need the "A" folder from a different Leopard installation with same level of updates as your machine or the proper ImageKit_tiger.pkg from somewhere. At the time of writing, the required folder has the following md5 on 10.5.2 with all security updates:

$ md5 /System/Library/PrivateFrameworks/GraphicsAppSupport.framework/Versions/A/Frameworks/ImageKit.framework/Versions/A/ImageKit
1786a69b42c828414dbd4b191dce1d47

The version according to Resources/version.plist seems to be 1.0.1 and I have NO idea where to get it from if not from a second machine. The iLife 8.2 update on Apple's website has ImageKit with version 1.0! The 10.5.2 Combo Update does not have the required ImageKit at all. My guess would be that it came recently with one of the Standalone Updates, if you have no access to a second machine, try your luck with one of these. You will need Pacifist for browsing the packages. Should you succeed, please leave a comment here.

In any case, after copying the A folder back to it's place it is advisable to repair disk permissions with Disk Utility.

Possible other ways to fix this:

• Check your Time Machine backup, if you are doing full backups, it may be there!
• Reinstall everything and hate Apple forever