Your project file may be experiencing some corruption. Did you insert each of these slidelets using the Insert menu or did you perchance just copy and paste them from the same one? I've seen that practice cause issues sometimes.
Try creating a new blank project and then insert a few test slidelets using the Edit menu. Do they work when this project is published? If so, at least you know your Cp install is fine.
Try hiding slides in your project as per suggestions in this post:
http://www.infosemantics.com.au/adobe-captivate-troubleshooting/basic-troubleshooting-techniques
It may be that the corruption is limited to one or more slides and you can resolve it by rebuilding those slides.