JEFFREY MCPHEETERS  You mention the app will not even launch fully? Have you tried creating a new user with no 3rd party prefpanes or startup items and then launch it from that user? Did you look at the logs? I would expect if you had tech support on the phone they already suggested all this, but just in case, I thought I'd pose the question. The one Mac I don't have is a late model 8 core Mac Pro.  
(Version 4.2.1)

DAWGDRUMMER  Does not work on my 2009 MacPro 8 core Nehalem with Snow Leopard. Of course Final Cut Pro does work just fine so I can continue my work. My advice is to avoid this software because the team that works on this must be dysfunctional. Photoshop, Illustrator, InDesign work just fine! Premiere Pro won't even open properly. Too bad I wasted my money!  
(Version 4.2.1)

GABBYN  I recently upgraded from the Creative Design Suite CS3 to the Master Collection Suite CS4. Everything runs great, with one exception: Adobe Premiere Pro, which is THE reason I decided to go with the Master Suite. I was so impressed with On Location to manage my rapidly growing stock footage library, which is part of Premiere Pro and you can't use it, if Premiere Pro crashes on launch. I spent all day on the phone with Adobe tech support, being routed deeper into their system three times before I reached the Premiere Pro expert. He was pleasant and patient and we tried everything he knew, but without success. He said, "it's an extension conflict with Apple, and they'll have to fix it before my program will work on a Mac.

When you invest $2,400 in software--this is not the "pass the buck" solution you expect. Waiting for some programmer to write some code in the hopes you might eventually be able to use this software. If I want it sooner, I'll have to pay $70 an hour to speak to Apple tech support. Then, today, I watched a tutorial on Premiere Pro CS4 on a Macintosh computer. Go figure! If you're on a Mac, I'd hold off buying this upgrade until the bug fix is in. If anyone has an answer, I'm ready to hear it.  
(Version 4.0.1)