Dude, I had EXACTLY the same problem. It drove me nuts. I installed CS4 Design Premium and everything worked except for Dreamweaver, which I needed the most. THe people at the Adobe.com forum for DW had no clue, so I started hunting, and found this:
http://kb.adobe.com/selfservice/view...1096&sliceId=1
This is some Adobe tech's complete list on how to diagnose and fix Dreamweaver CS3 issues. It works for CS4 as well, because I got down to the place where you make the Mac reboot in Safe Boot (and this forces the Mac to run a disk check and a permissions fix prior to loading OS X), suddenly Dreamweaver started acting like, "Hey, whats the problem?"
I hope this helps.