Some versions of Keynote are creating problems with Mountain Lion.
A work around that is helping most users:
Delete iWork completly, you will need an uninstaller to do this properly, I use Appcleaner or purchase Appzapper to do this.
If you have an iWork DVD disc, reinstall iWork and dont update, turn off auto updates.
If this was an app store purchase log into the store and install iWork 9.3 http://support.apple.com/kb/HT5534
Post back to let others know your experience