Some movies [.iso files] wont play on NitoTV ?

NitoTV wont play some movies (e.g. Pink Panther 2, Harry Potter - Goblet of Fire). I made .iso files from my DVDs. The files are stored on an external drive. The same .iso files play fine using XBMC. So it is not the file themselves. However, XBMC playback is noisy and has black horizontal lines, so I prefer to use NitoTV which has a clear video while playing. Any ideas what the problem might be ? Thanks

Has the Smart Installer been run?
http://wiki.atvflash.com/index.php?title=Smart_Installer