that screen sounds like a memory issue. i had that when installed vista right at the end of installation on my old agp system. i had 4 sticks of ram took two out then it installed fine then put them back in again. theres been talk about raising mem voltage dnt know if you have but if you havent try that first

Hope it stays stable. Yes you need 64bit drivers
One thing though had you set the voltage right (and saved it) before you installed vista? If not then i'd give it one last install.