There are multiple lengthy threads on the Apple Discussion Forums and the Adobe Forums regarding font problems after updating to Mac OS X 10.6.7.
The majority of the problems reported involve using OpenType fonts. Mac OS X 10.6.7 seems to introduce a bug that prevents some OpenType fonts from rendering on screen, printing, or being embedded properly in PDFs. Symptoms include documents failing to open, fonts being replaced with gibberish, fonts being randomly vertically stretched, “invalidfont” errors when printing, and hanging when attempting to save/export to PDF. These problems have been reported with various applications including Adobe Creative Suite, QuarkXPress, Microsoft Office, iWorks, iLife and even TextEdit.
Apple has yet to publically acknowledge the bulk of these OpenType font problems with Mac OS X 10.6.7, however Adobe did post an official Knowledgebase article stating they and Apple are working on a fix for Flash OpenType rendering problems introduced with 10.6.7… http://kb2.adobe.com/cps/896/cpsid_89637.html
The rumor is these OpenType font problems were introduced by changes Apple made to address unspecified security vulnerabilities with Snow Leopard.
Downgrading to Mac OS X 10.6.6 fixes these OpenType font problems 100% of the time. There are a handful of other workarounds that some people have had luck with, including frequently clearing font caches and converting the OpenType fonts to TrueType, but ultimately the underlying problem will need to be resolved by Apple. Unfortunately some new Mac are now shipping with Mac OS X 10.6.7 preinstalled, and they can’t be downgraded.
I personally am not recommending anyone update to Mac OS X 10.6.7. These problems are too widespread. For example, several people posting saying they couldn’t even open some PDF tax forms posted on the IRS website.