When creating a NTriplesContext with a file as argument it will not create the context in the right place under windows. For example when creating the content in C:\Documents and Settings\Rob Kooper\Desktop\data\ntriples.txt or in URI file:/C:/Documents%20and%20Settings/Rob%20Kooper/Desktop/data/ntriples.txt it will create a file in a directory called c:\Documents%20and%20Settings\Rob%20Kooper\Desktop\data\ntriples.txt. Note how it keeps the %20 in the file.