If Aperture 3 isn't starting up properly or performing normally, try these basic steps to troubleshoot the situation. Please note that these steps aren't exhaustive and are not intended to cover any specific issue. These are fundamental, basic steps for getting Aperture into good working order, and are the steps most often suggested by AppleCare Technical Support.
Library first aid typically solves most issues experienced by users of Aperture Exporter.
Rebuild the Aperture Database
Hold Option + Command on your keyboard while opening Aperture. This will bring up the Photo Library First Aid dialog. Click Rebuild Database then the Rebuild button.
For more detailed information, see Apple's support article on Aperture troubleshooting.