Adobe did testing across the CS4 line atop the new Apple OS. There are a few minor issues documented... see blogs.adobe.com or individual product support pages.

Adobe did testing across the CS4 line atop the new Apple OS. There are a few minor issues documented... see blogs.adobe.com or individual product support pages. Most people find it just works. It's quite possible that someone has a minority experience, where it doesn't work. First steps are to check the integrity of the applications (it's legit CS4 direct from Adobe?), then any customizations to the system that may cause it to act differently than others. It's to everyone's advantages to document all meaningful Snow Leopard differences.