Flash CS4/CS5 PNG export looks bad

Not sure why, but when I export my movie as a PNG sequence (using Flash CS4 or CS5), the colors in the resulting PNGs are very washed out and flat. I have imported some graphics with alpha channels from Fireworks.

I have tweaked all the export settings that I can find. The filter type is set to “none,” smoothing is off, and the color mode is 24-bit with alpha channels. No dithering or interlacing. Always looks muddy and flat, and gradients have banding that isn’t present in the original. I’ve got CS4 on my PC and CS5 on my Mac, they both give the same bad result.

I’m doing this as a workaround for CS4/CS5’s compromised QuickTime export (export framerate is not maintained), so this quality issue is pretty disappointing.

Anyone have a workaround for this workaround? Here’s a comparison of the Flash workspace (left) and exported PNG (right) from CS5: