After installing (in Mambo) zOOm gallery and trying some things, it seemed to work, but for some unknown reason, it left the content management system a tad askew.
The zOOm component installed OK, but the problem was that I could not add more content afterwards. No matter what I tried. The irony is that I wanted to add an announcement of the new gallery.
Finally, after uninstalling it and redoing the upgrade (I’ve kept a db dump and the files from before the upgrade) and the patching of Mambo, I am finally able to post new content. I might give it a try again later today, when I am more rested (it is 4:45am now in Lima, Peru).