My dad recently had some serious problems with his Aperture library. The first issue was with landscape and portrait and stretched / squashed preview images. Many preview images also appearing very blurred.
Rebuilding the library did fix this issue. but it reappeared again after a while.
Other previews only show up on a quarter of the screen, rather than strtching over the whole screen, filling the rest with distortion.
The next issue which seems a bit strange is with the amount of images. Opening Aperture 3.1.1 results in a different amount of images every time it is opened (roughly 20.000 images). Sometimes with 3000 images more all of a sudden. These images are duplicates of originals as well as copies, and show up next to them. with up 30 duplicates of a single image. selecting one of the duplicates of one image and trying to delete them, deletes all the duplicates of that image which have been randomly created. Deleting 4 duplicates sometimes only shows then just 1 or 2 images in the trash.
Rebuilding the permissions as well as rebuilding the whole library, resulted in some of the duplicates vanishing. But after a relaunch of the application, more duplicates reappeared.
After any relaunch Aperture also starts to reprocess about 200 pictures, even when nothing was done to the library.
A preview image that shows the randomly created duplicates can be viewed from the link below. this also shows the small non-link icon (?).