Sorry, my bad, I hadn't finished my thought before I hit submit. Focus was torn between too many things.
Anyhow, I run CS2 on windows. I have had it happen before so that when I tried to save for the web, the white turns a yellowish color.
I tried what seemed like zillions of things within photoshop. The way I finally fixed it is by going in to my control panel, and fixing it through the adobe gamma thing. It's been a good while since it happened, so I can't recall the specifics of why that fixed it.
But it did.
I don't know how that translates to a mac, or if it will even help.