It might have been a missing font but that shouldn't keep the file from opening. It could also be a missing picture or video. Try exporting from keynote again and see if it gives you any document warnings. if you get any warnings then post them here and i can try to help some more.
Are you able to upgrate to 10.9? Did you buy keynote from the app store? If so, you could try the upgrades and see if it's better. When I upgraded today it put the older version of keynote into an iWork 09 folder so you can probably go back if it doesn't work and you don't like the newer keynote.