PNG Files In Shake?
 

For some reason I can't work out how to work with transparent PNG files in Shake. When you bring in a PNG file (with transparent components) into Shake, it displays these transparent sections as white (not see through).

When you bring in a TIFF however, it automatically makes the transparent sections transparent.

For example, say I have a blue background. If I bring in a PNG file of a black ball with transparent background and put it over the top of the blue background node, the black ball (and a white background) will only be visible. However, if I bring in a TIFF instead, the transparency info comes with it. I hope I'm explaining this OK.

As far as I knew, PNG files should be treated the same was as TIFF files in Shake. What am I missing?