[The following is a "guest post" by my friend Ed Klemz from Central Coast Solutions.]
On 2/1/2012 Apple resleased Security Update 2012-001 for OS 10.6 (Snow Leopard) - DO NOT install it if you use any older software (pre-CS5, Quark 8, Suitcase 3, etc.) as it will disable the 'Rosetta' code that allows older PowerPC applications to run. If everything you run is new then it's not an issue - but I know the bulk of you out there still access older Quark and InDesign workflows when needed, and many older support apps and utilities are rendered unusable as well.
If by chance you did apply this update and it is causing issues, your machine will need its OS reinstalled and updated to appropriate levels.
If you get a Software Update notice, click the 'Details' button and you'll see the list as shown below, simply uncheck the Security Update 2012-001 and allow the others to update. Be careful with all future updates as well...as it will re-check itself next time Software Update runs.
If you ever have an update notification pop up, feel free to let us know before you apply it and we'll let you know if it's OK to do.