What is a font cache file?

The operating system and certain applications use font caches to keep track of installed fonts. Problems can occur If a font cache becomes corrupted, for example: fonts not appearing in an application font list; or wrong fonts; or missing fonts in documents. The best solution is to delete the font cache file(s). This is OK as they are automatically restored on system restart, or on relaunching an application.

How to locate and delete your font cache

Operating system font caches

The Mac OS X operating system has numerous font cache files.
To automatically reset all font cache files:

Mac OS X 10.4 (Tiger) and later
Restart in Safe Mode (also known as a 'Safe Boot'):
Shut down the computer.
Press the power button.
Immediately after hearing start-up tone, hold down SHIFT key.
Release SHIFT key after Apple logo and progress indicator.
Restart the computer without holding down any keys.

Older Mac OS X versions, or to manually remove font cache files
they can be found in the following locations:

com.apple.ATS.System.fcache
com.apple.ATSServer.FODB_System
/Library/Caches/com.apple.ATS
/Library/Caches/com.apple.ATS/501/Classic.fcache
/Library/Caches/com.apple.ATS/501/Local.fcache
/Library/Caches/com.apple.ATS/501/System.fcache
/Library/Caches/com.apple.ATS/501/FondResourceCache
/Library/Preferences folder: com.apple.ATS.plist
/System/Library/Caches/com.apple.ATS.System.fcache
/System/Library/Caches/fontTablesAnnex

Windows 2000, XP, Vista, Windows 7
Font cache files for Windows operating systems are located here:
C:\Windows\System32\FNTCACHE.DAT
Delete this file, and restart your system.
A new FNTCACHE.DAT file will be created on startup.
 
Application font caches

Mac Office
\Users\User_name\Library\Preferences\Microsoft
Delete 'Office Font Cache (10)' or 'Office Font Cache (11)' file.

Adobe Acrobat, Creative Suite
Search for 'adobefnt*.lst' file(s). Delete all these files.
(note this applies to Mac OS X and Windows systems)