O.K. I've put the test gallery here for now (please let me know when you've seen what you need to so I can take it down). If you need it, I can archive the whole gallery and provide a link to the resulting zip file.
I am still using OS X 10.6.8.
I have tried clearing the browser caches but it doesn't help.
imagePreloading is unset, but specifically setting it to "PAGE" or "NEXT" does not help.
The demo gallery you posted a link to works fine for me - I do not see the problem that I am having.
Specifically, what happens is that when transitioning to a new image, the old image seems to fade out properly and the next image begins to fade in but then the image goes completely black for a short bit and then snaps back all at once. The issue is by far worst in Chrome (33.0.1750.152), less so in Safari (5.1.10) and does not occur in Firefox (27.0.1).
Thanks again.