If, once you’ve restored Keynote or iWork from your Time Machine backup disk, you get the error “Files that iWork needs are missing” when you try to run any of the iWork applications, it might be because you haven’t restored the preference files found here:
/Library/Preferences/
such as:
com.apple.iWork.Keynote.plist
com.apple.iWork09.Installer.plist
etc.
Copy those over too and you should be ok.