Apple released an update to Aperture today.
From Apple:
Recommended for all licensed Aperture customers, Aperture 1.5.2 improves overall reliability and performance in a number of areas of the application, including contact sheet printing, Smart Albums, watermarks, Lift & Stamp, image export, and versions using an external editor.
Important Note: Aperture updates, such as the Aperture 1.5.2 Update, cannot be used to update previously downloaded versions of the Aperture Trial. The current version of the Trial delivers Aperture 1.5.2, so no update is necessary.
http://www.apple.com/aperture/download/
