oh sorry, the crashing script is without this line  if len(items) > 0 with this line it dos work.

def update_interface(dia):
    items = RLPy.RScene.GetSelectedObjects()
    newname=items[0].GetName()
    print (newname)

… well I have found out more ….. already this little script lets iClone crash, when I load a new Project or delete the seleted item …..

class EventCallback(RLPy.REventCallback):
    
    def __init__(self):
            RLPy.REventCallback.__init__(self)
            dia=0

   
    def OnObjectSelectionChanged(self):
            print("selection changed")
            update_interface(1)
            
            
    def OnObjectDeleted(self):
            print("event Object Deleted")
            update_interface(2)
            
def update_interface(dia):
    items = RLPy.RScene.GetSelectedObjects()
    if len(items) > 0:
        newname=items[0].GetName()
        print (newname)


events["event_callback"] = EventCallback()
events["event_callback_id"] = RLPy.REventHandler.RegisterCallback(events["event_callback"])

But, if I add a line to update_interface(dia), I can load also a new Project or delete an item:

def update_interface(dia):
    items = RLPy.RScene.GetSelectedObjects()
    if len(items) > 0:
        newname=items[0].GetName()
        print (newname)

I think, this should not happen, that this dos crash iClone, if there are no items selcted. There could be an error message.

Just to clarify: you mean you actually load a project, while a script is running?

I would think that that would cause the state of the environment to change including variable bindings, etc. So that will cause a crash.