Ditto (last update) does not run correctly under Windows 10 preview: sometimes it does not want to start, sometimes it starts but it does not remain active.
The application wasn't released to fully support Windows 10, because the OS hasn't been officially released. You're trying to run an application on an unfinished version of Windows. Almost all applications have issues running on Windows 10 until the OS has been fully developed and the developers updated their applications to support Windows 10. You can address this issue on the discussion forums on SourceForge.
Discussion: http://sourceforge.net/p/ditto-cp/discussion/
