The general approach at this time is to ask if you've checked for any problematic fonts (all languages) with Apple's Font Book (look in the Applications folder). Find and remove all duplicates also.
Start there to be sure all fonts that are in play come out with a clean bill of health.
Don't hesisate to perform wholesale deletion of old and/or little used fonts - be skeptical of anything that has come from Office 2008, including those related to an Equation Editor installation.
By all means be sure any 3rd party apps AND plug-ins are Snow Leopard compatible.
An additional measure is to clear the existing font caches:
http://www.macworld.com/article/139383/2009/03/fontcacheclear.html
That said, 10.6.2 release notes have this to say about fonts:
http://support.apple.com/kb/HT3874
Fonts fixes provided for:
• an issue with font spacing
• an issue in which some Fonts are missing
• font duplication issues
• an issue with some PostScript Type 1 fonts not working properly
Good luck in any case.
