With the latest patch, I've started having textures disappear in 64bit as well. Before the patch I was only seeing some pink textures.
I have noticed that they vanish and reappear due to very slight changes in the viewing angle. Notice in the pic below you see the normal texture, then the texture blurs, then it vanishes, then the skin blurs. And if I move the viewing angle back the texture will re-appear. HTH.
ContraTempo
Carpe DM
Seize the Dungeon Master