In WiX v3, Light automatically runs validation, Windows Installer Internal Consistency Evaluators (ICEs), after every successful build. Validation is a great way to catch common authoring errors that can lead to servicing problems. That is why ICEs are now run by default. Unfortunately, there is an issue that can occur on Windows Vista and Windows Server 2008 that can cause ICEs the to fail.
For details on the cause and how to fix it, see the additional resources in the sidebar.