I'm under Vista, Visual Studio 2008
Running the packager, after pressing the OK button on the assemblies window, I get an error message with a trace and a seSecurityPrivilege problem or something like that for the current process (packager). I suspected (-again-, because I had the same problem many people had when installing the SDK too) the User Account Control of Vista preventing the package from doing an insecure operation. I disabled temporarily the UAC and hourra, it worked well this time.
So, I want to inform you that there is a problem in the installer AND in the packager application itself regarding security. Test your app with Vista, having the UAC enabled. User Account Control is a new feature of Vista and security rules must be respected by all developpers. Turning UAC off is NOT a solution.