OK, so there are updates for the three apps named iWork '08.
As I do not like folders in my Application folder, I Keynote, Pages and Numbers out of the iWork '08 folder, and deleted the empty folder.
Now Software Update says there are no updates available, as it apparently looks for that folder.
The stand alone updates act the same.
Is there a way to work around this stupid behaviour?
(instead of recreating that folder and put these apps inside just to get the latest updates, and then delete that folder afterwards again...)