Yes, all of them (backlinks are missing globally). At the moment this new site only has five pages, but they are all accessed from the start page through a hierarchical menu. No page is listed als "orphan". I have double checked that both anonymous and registered users have the right to view backlinks.
Found the solution myself. Buried deep on Admin Wiki Page there is yet another checkbox that has to be set. Actually, more than half a dozen or so, otherwise backlinks will not show blog entries or file gallery references...