CP5.5 - yellow highlight doesn't show in image

I'm getting a strange result when I publish a project created in CP5.5.  The screencapture is of a search screen, and the criteria is highlighted in yellow wherever it's found.

The yellow shows up in Captivate, and when I export it to Paint Shop Pro, but not when it's published or previewed.  I've experimented with increasing the slide quality (it's captured in 8-bit), to no effect,

I tried editing it in Paint Shop Pro, flattening the layers, and saving it back - no change.

Any ideas?