Sorry for inconvenience, but could you please try two things:
1. Use any other computer to test the page and check whether it loads all images as it should.
2. If possible, provide me with the URL for the images that are not cached.
Also, you can probably try to copy any imageset from ProgramFiles/9Rays.../graphics folder to your web site and make FlyTreeView to use this custom imageset. So it will be easy to detect the exact reason of the problem.
Thanks in advance.