Huston, I have an annoying problem that is hard to explain. I'm still working on my File view tree, all is working in terms of display and now drilling down (leafs load lazily). So, I've moved on to editing them. I was trying to store the TreeItem as a File (and created my extended class to cope with the laziload). However, I've also created my own TreeCell, to ensure the file is converted to and from a String; via a setConverter - String Converter