I've got the same problem with SAAC on Vista: failure to load and 50% CPU usage. SAAC v1.2 was tested on XP Professional SP2 before it's release, but not even compatibility mode will get it to work normally. I'd hate to have to go back to XP just to play this game with SAAC, and without it, I don't have that degree of control I once had.
I doubt there'll be a v1.3 with full Vista support out any time soon. If anyone has any alternatives besides the in-game control system, I'd be happy to hear them.
BTW, my system is a 1.6GHz Core 2 Duo with a GeForce Go 7600. I doubt setting the affinity will do anything, but I'll test that theory anyway.