Thanks for the suggestion, Rod! It led me down a path where I finally found my answer. For some reason, the videos I was trying to convert wouldn't do so in the Flash converter that came with Captivate 5.5. I did stumble across the converter for Captivate 5 still on my computer, and using that converted most of the files. The few that still would not convert, I had to get from the video creator in Flash format.
Not a real solid answer, but at least I got what I needed!