Keynote 09 (5.2) won't open in OS 10.7.5

The camera won't let me insert the screen shot (grr). Sigh. Ok, trying to open Keynote from iWork 09 (version 5.2) on my iMac with OS 10.7.5. First it said it just wouldn't open so I reinstalled it. Now it says "An unexpected error has occurred. Please quit and reopen Keynote." Of course it doesn't really let me "reopen" Keynote - it just gives me the error again. Any clue, friends, on why this is happening or, more importantly, how to fix it? True, I haven't used Keynote much since my company uses that other presentation software (shhh).

Help?

Pam