"Keynote cannot open because of a problem"
When I try to open Keynote 5.0, it immediately closes itself and I get the above error message. The dialog box then states to reinstall Keynote. I have OS X Lion, downloaded through the App Store; Keynote was a part of the bundle. It looks like I can't download Keynote a la carte from the App Store, though. Do I have to download and reinstall Lion all over again, just so I can reinstall Keynote? I'm confused.
MacBook, Mac OS X (10.7.5)