THIS IS THE FIX FOR THIS PROBLEM.
Downgrade to the previous version of Keynote and this problem WILL GO AWAY.
1. Find your iWork 9 DVD. If you downloaded iWork from the App store and do not have a disk, then you will need to find a disk. I don't know of any way to download an older version of iWork from the App store. Try eBay, try a friend, try the Apple store.
2. Remove iWork 9.1 using the script supplied by Yvan Koenig. Just deleting iWork is NOT enough - you need to clean up all the iWork files or this won't work. The script found on this server:
https://public.me.com/koenigyvan
Look in the folder called "For_iWork", then "iWork '09" and then download the file called "uninstall iWork '09.zip". When that has downloaded and opened, click RUN. Wait several minutes while it gets rid of iWork. While it's working the button will say "Stop" and when it's done the "Run" button will reappear.
The script does not remove your personal templates stored in your user/library/application support/iworks folder, so you don't have to worry about losing those.
2. Reinstall iWork 9 from your disk.
3. Next you'll want to update iWork to version 5.05. You can get this here. http://support.apple.com/downloads/#iwork.
There are FOUR update packages: 9.0.1, 9.0.3, 9.0.4 and 9.0.5. Download and install them one at a time, in order. Yes, I know these are version 9.0.1+ and we're upgrading to 5.05 - who knows what's with that. Just roll with it.
4. The first time you open any iWork app (Numbers, Keynote or Pages) it will ask you to upgrade to 9.1. DO NOT DO THIS and check the box indicating NOT to be reminded again.
Any time in the future that you do a software update it will offer to update iWork for you. Make sure that each time you DO NOT update iWork.
If it did not work, check the version number on Keynote (go to Keynote > About Keynote). If it says version 5.1 then you didn't properly uninstall the old iWork. If it says version 5.0.5, then it should be working. If it's not, then this fix didn't work for you and you should definitely post a message to this forum because you would be the first person it didn't work for.
Finally, if you have downgraded your version, then let Apple know by visiting the Keynote feedback page and providing information here:
http://www.apple.com/feedback/keynote.html