I'm just trying to build a simple update (which I have done before) for an iphone app, but now for some reason I'm getting this error. Can anyone tell me what it means?

Command/Developer/Library/Xcode/Plug-ins/CoreBuildTasks.xcplugin/Contents/Resources/copyplist failed with exit code 127
sh: plutil: command not found

Here are the Build Results:

CopyPNGFile /Users/me/path/build/Dist-iphoneos/MyApp.app/img_000.png images/img_000.png
    cd /Users/me/
    setenv COPY_COMMAND /Developer/Library/PrivateFrameworks/DevToolsCore.framework/Resources/pbxcp
    setenv PATH "/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin:/Developer/usr/bin:/System/Library/Frameworks/JavaVM.frameworK/Versions/1.6/Home/"
    "/Developer/Platforms/iPhoneOS.platform/Developer/Library/Xcode/Plug-ins/iPhoneOS Build System Support.xcplugin/Contents/Resources/copypng" -compress "" /Users/path/images/img_000.png /Users/me/path/build/Dist-iphoneos/MyApp.app/img_000.png
sh: dirname: command not found

CopyPlistFile /Users/me/path/build/Dist-iphoneos/MyApp.app/Entitlements.plist Entitlements.plist
    cd /Users/me/
    setenv PATH "/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin:/Developer/usr/bin:/System/Library/Frameworks/JavaVM.frameworK/Versions/1.6/Home/"
    /Developer/Library/Xcode/Plug-ins/CoreBuildTasks.xcplugin/Contents/Resources/copyplist --convert binary1 Entitlements.plist --outdir /Users/me/path/build/Dist-iphoneos/MyApp.app
sh: plutil: command not found