Karl, I have been experiencing a couple errors that may be bugs. When I create a gallery of images under the Galleries menu item and the title contains more than one word and I navigate to that gallery, I will get a 404 error. When I shortened the listed item to one word, navigation works fine. While trying to recreate the error, which it did happen again, I am unable to navigate to the gallery after changing back to a single word. 404 error. I will be working on this to see if I can come to a conclusion but it seems to be pretty consistent.
I changed the name completely (one word) and I am able to navigate to that gallery.