How do I know this? Because you get this error if you have a 2000 Active Directory:
UserProfileApplication.SynchronizeMIIS: Failed to configure ILM, will attempt during next rerun. Exception: System.Security.SecurityException: The Kerberos subsystem encountered an error. A service for user protocol request was made against a domain controller which does not support service for user.
If you want to move to SharePoint 2010, you must upgrade your active directory to 2003 or higher.
Chris