Aperture will not open after update? What do I do?

What happens when you attempt to launch the app? Does it crash?

I have the same problem and it doesn't crash but says that it's still "installing" the update but it's been "installing" for over 18 hours now! Any suggestions?

Mgoss, quit the installer or App Store/Software Update (depending on what you're using to update) and restart your machine. With Aperture closed, drag the Aperture application to the trash, then reinstall Aperture from your original media and, if necessary, update again.