Why does the DDBLT_KEYSRC cut out my imagery? I set the color key to DDCKEY_SRCBLT with both high and low color spaces set to 0. When I blit to the back buffer using a simple black and white checkered image the white checkers don’t show up, hence they are cut. Why?

For some reason the color key blits don’t work with the back buffer. But they do with off screen surfaces. But I’ve read somewhere that not all graphics cards support off screen surface color keys.