I had an error message saying open iPhoto and fix the library. When I opened iPhoto, it asked what library to use and game a choice (of the one and only library I had). After that, the sync was fine (with iPhoto still open -- not sure if that matters). My guess is that iTunes updated from iPhoto to find the pictures.
[I may have moved a few pictures since I was playing with Aperture-3 a week ago.]
Mine it taking a long time to sync. Stuck on "Optimizing 3266 of 3266" for the last hour or so. But it seems to be syncing music cuz the number keeps going up. I'm afraid to cancel and have to start over or corrupt something. I guess I should be patient.
I am using Aperture 3 and the albums are not syncing correctly with the iPad. It may be an iTunes 9.1 issue rather than the iPad. Problem is that it does not sync all items within the album e.g. 80 photographs in the album (as reported in Aperture) and only 37 reported in iTunes and synced with the iPad. Created the exact same album in iPhoto (photos in the same location) and all works correctly.
Irritating as I am using Aperture as my main photo management tool and this means I must reimport them into iPhoto and create albums etc. in order to ensure they are synced correctly in iTunes and the iPad.