You did not answer my previous question, if file vault is turned on. File vault is the Mac OS encryption for security. It is activated in the System Preferences "Security and Privacy" panel. If it should be turned on, turn it off. I did not mean Aperture's vaults used for backup.
Have you tried everything in the
Aperture 3: Troubleshooting Basics ?
BTW: can you import by dragging from the Desktop into Aperture's window?
To be sure if reinstalling can help, try to launch Aperture from a different user account. Start with a new, empty library and import some images.
If it even from a new user account does not work, run a hardware check, repair the file system, , reinstall Aperture, reinstall your Mac OS.
But if Aperture works from a different user account, you need to check all con figurations in your account that might be different, remove Apertures presets (not only the preferences), disable login items, remove older plug-ins.
Post back, when you know, if Aperture works from a different user account.