I have almost completed a new tour and need to add another scene to it. When I add the scene, it goes into the bottom of the list (which is what I expect) But when I try to move that new scene up the list I get a message box stating "Encountered an improper argument" and I have to shut off the program unsaved because all of the images in the scene list disappears altogether. When I restart TW, they are back in as before and without the new image.

Is there a problem with the software or am I doing something incorrectly?

You should be able to reorder without error. That said, I have also run into this problem before. You can try to adding the scene and saving the the tour as a new name, then attempt the reorder and save again.

Regards, Smooth