Finally got x64 RTM installed tonight and everything worked out...mostly.
My problem is that I have to run almost everything as an administrator. If I don't, the app will open briefly, then close. But it stays running under just a few megs of RAM in the Task Manager.
Happens on Firefox, IE 8 x86, Thunderbird, Cisco AnyConnect, etc. I tried reinstalling all these apps by running installers as administrator, compatibility mode, etc. Still requires me to run every app as an admin.
And yes, my account is an administrator.