Windows not refreshing correctly on OS X

Hello, I am running Unity on Snow Leopard with an Nvidia 8800 video card. My problem is that before a window will draw itself, I have to move the window a little bit, otherwise it just sticks on the first frame. For instance if I open the Asset Store Window, it will only show me the “Connecting” image until I move the window. Same with color pickers, I click on a color, the color picker opens up, but the window won’t redraw even if I’m selecting colors.
Does anybody have any ideas? It’s driving me insane!

I fixed it. If anyone ever gets this problem, on my machine it was caused by running a utility program called Shades which allows you to dark the screen. I believe it works by putting a semi transparent quad across the entire screen, which Unity doesn’t like.