OK, now we are getting somewhere. As someone posted earlier, I was indeed looking at the wrong File Manager. I was looking at the one under the "Host" menu, instead of the one under the "Admin" menu. Once I went there and resynched the folder, I could see the gallery folders and their permissions.
However, I still have a problem. When I select the root "Gallery" folder and look at the permissions, "Administrators" has View & Write rights. And "All Users" has just View rights. I am in the "Administrators" role, and yet I still have the problem of not being able to upload files. When I select the sub-folders of the "Gallery" folder (including the Albums and "_thumbs" folders), the same Folder Security Settings are in place - which looks right, as they should be inherited from the root "Gallery" folder, right?
Anyway, I would appreciate any further comments or suggestions. Thank you.