Yes I found that error. I'm going to attach a new version that has changed many things but needs really to be tested. This one allows attaching scene nodes, and objects to them, move them in the scene. But for now does not save them. I have changed the whole process and structure. And after a test that says everything added up to now is working and has no error, I would add some new changes, first of all saving the scene nodes and then managing the static geometry.
here is the link to new version:
http://www.mediafire.com/download.php?2ojlwty2wnwand if any one is interested in what the process of using this scene designer would be, I have to say that, I am designing this so that everything designed with this program is stored in a xml file and a resource folder in addition. After that the game developer can use a class coming with this designer to easily load everything inside this xml file into an instance of Axiom Root object.