The prolem is solved. Chris from NCH tecnical support answered me: "it seems the issue is that the file's name is too long and that is causing the issues with the program. Would it be possible for you to try using shorter names for the songs and test again? The file name length is a Windows limitation, if the file name exceeds the supported character limit it will simply fail during the writing process. He was right. When the problem happens I just shorten the album title and it is OK. As I'm ripping classical music on many tracks thera are a lot of data / names - the orchestra, the conductor, the author and than allso various solists...- the file names in same cases could be too long.