image-dired question

[Steven Arntson]

Emacs 24.3.1, Ubuntu 13.10

I'm just learning about image-dired, and am having a quirk of
functionality that has stumped me. In a dired buffer, I mark several
files (such as a-file01.JPG, another-file02.JPG, and five or so
more). C-t d opens them in a neat-looking row, with the first flashing
because point is on it.

RET opens this first file in another buffer---very neat!

However, when I hit space to move forward to the next image, point goes
to the end of the row, and the minibuffer tells me "no thumbnail at
point." If I use back-arrow key or C-b to try to backtrack to any of the
other thumbnails, point returns to the first one. So far I haven't been
able to expand anything but that first thumbnail.

Thank you!
steven arntson