This may happen with photos that you imported into the Aperture library before installing the update. To resolve the issue:
- Select one or more affected photos in the Browser.
- From the main menu, choose Photos > Reprocess Originals.
- In the Reprocess Photos window set the following options:
- Set "Which photos do you want to reprocess?" to "All photos"
- Set "Do you want new versions created for the reprocessed photos?" to "Reprocess existing images"
- Click the Reprocess Photos button to finish.