Hello Andrew,
There are a couple steps that I would recommend following in order to get Keynote back up and running again. First, verify the fonts installed on the system with the Font Book application, so as to isolate and remove any problematic fonts that may be the source of the issue.
Mac Basics: Font Book
http://support.apple.com/kb/HT2509
Validate problematic fonts
If there is an issue with one of the fonts, you can use Font Book to validate all fonts or a specific font. Validating checks for potential issues.
To validate all fonts:
- Log in as an administrator user if you want to use the "Remove Checked" button described below. Non-admin users can also validate fonts, but only remove ones in their home folder.
- Open Font Book.
- Click "All Fonts" in the Collection column.
- Choose Validate Fonts from the File menu.
- If Font Book identifies an issue with fonts, you can click the alert icon at the bottom of the window, then click the "Remove Checked" button to remove problematic font(s). You should then re-install the affected fonts from the original source. If the font still does not pass validation, contact the creator of the font or the company that you obtained the font from for assistance.
If the issue is still unresolved, or your fonts are not appearing correctly in Font Book, as well, try booting the system to Safe Mode by holding the Shift key while turning the computer on. Once logged in, restart the computer normally. This will, among other things, remove the system's font caches (this will not remove or delete any actual font files).
Mac OS X: What is Safe Boot, Safe Mode?
http://support.apple.com/kb/HT1564
To perform a Safe Boot, press and hold the Shift key immediately after your Mac starts up. Continue holding down the Shift key until a gray Apple logo appears on the screen.
Starting up into Safe Mode does several things:
It moves to the Trash all font caches normally stored in /Library/Caches/com.apple.ATS/(uid)/ , where (uid) is a user ID number such as 501 (Mac OS X v10.4 or later).
Cheers,
Allen