Is it any particular action effect or any of them? Have you tried creating a new user to see if you get the crash under the new user? It takes a few minutes to create a new user (and you can delete it afterwards) and it would go a long way towards determining if it's a problem just with something you've installed recently OR with your entire system.
I created a new user, without iCloud integration, and fire up my Keynote on play mode.
Everything worked OK, I did some minor changes and had no further problems.
So I switched back to my original user, and duplicate my Keynote file outside iCloud and since then, seems like the freezing problem is no longer happening.
Ok, if it's just that user, then it would have to be an application you installed recently (or maybe even awhile back) that's interfering with what Keynote is trying to do. Have you installed anything related to graphics or images? Might be something that would appear unrelated, but might as well check those first.
Is there chance that the screen saver might be the problem?
To answer the question:
I bought Keynote about two weeks ago through the Apple Store, so I'm going to list all apps related to graphics (from recent installed to older):
- EazyDraw 3.5 (old version), not an identified developer.
- Fotor (from the Apple Store)
- XQuartz (X11)
- DivX Plus Player
- Flip Player
- Microsoft Silverlight
- Microsoft Remote Desktop Connection
- Snagit (from the Apple Store)
- VMware Fusion