No, the item count is still there in each event.
Then try Frank Caggiano's User Tip, if there is an invisible filter.
If that does not bring the photos back, repair and rebuild, if necessary, but don't rebuild without a backup.
I've tried an Aperture update and it says there aren't any available.
With 10.6.8 you should be able to upgrade to 3.2.4 as well.
How did you buy Aperture? If you bought a boxed version, or downloaded the Trial, then "Software update" from the Apple menu should show an update. Or you can download it from the Apple Support page. Aperture 3.2.4
If you bought from the AppStore, you'll have to update using the AppStore, but in that case I do not know, if it still will be possible.
regards
Léonie