updated 11:10 am EST, Fri February 3, 2012
Apple said to be aware of problems
The separate Security Update 2012-001 download for Snow Leopard users is breaking apps that depend on Rosetta, according to complaints. Rosetta allows PowerPC-based apps to operate within Snow Leopard. Programs such as Eudora 6, Acrobat Pro 7, Quicken 2007, and Office 2004 will reportedly crash, freeze, or exhibit other unexpected behavior, such as failing to print documents.
Apple is said to be aware of the issue, but there is no timeline on a patch. People who need apps working earlier have two options, the most extreme of these being reinstalling Snow Leopard and updating to v10.6.8 while rejecting Security Update 2012-001. An unofficial app called RosettaFix may solve some problems by replacing files updated by 2012-001 with previous versions, but glitches persist in apps like Eudora 6, Acrobat 7, Photoshop CS2, and AppleWorks 6.
Apple has gradually drifted away from PowerPC support. Leopard was the last version of OS X to run on Macs with PowerPC chips, and in Snow Leopard, Rosetta was left out of default installations. Lion has no support for PowerPC apps whatsoever.