Basically, the flagged correct answer in that thread seems to involve doing the following and then reinstalling:
(My suggestion would be to create a folder on the desktop as a temporary residence for the following files and folders to mode).
In your home directory, remove iWork plist files from /Users/your_account_name/Library/Preferences folder, which would be for the iWork applications.
Move the folder /Library/Application Support/iWork '09 to the temp folder you created.
Move the folder /Applications/iWork '09 to the temp folder.
Reinstall the program. Something got hosed in the installer the first time around (it happens). It worked for the OP in the linked discussion.