Blurred images with background knocked out displaying as white transparent boxes

I used the new presentation tool to give a talk a few weeks ago and it looked great, and loved using the timeline to animate! I just found a small display bug that didn't used to be there. I imported some black and white bitmap illustrations I'd made previously, knocked out the white background in Express, then made faux dropshadows by duplicating the images, adding blur and adding transparency to the black blurred image to look like a shadow. The blurred and knocked-out images are now displaying as ghosted white transparent boxes and the images don't display correctly ('faux' dropshadows are gone, replaced by white boxes). See screenshots -- I added some older screenshots of the original created a few weeks ago so you can see how it used to look.