Keynote Slideshow displays in reverse sequence

Why does my Keynote slideshow display the slides in reverse order from the order in which placed them?

I have burned 3 CDs with the same result that shows the slides in reverse order. During last September I bought my iMac and the following week I put together a slides show in Keynote for a presentation for my wife. It turned out beautifully.

After not using Keynote since, last week I put together another slideshow of a two week trip and burned CDs. Although I put it together in the same way that I had done with the September slideshow, the slides were shown in reverse order - the one that was placed first was shown last and the one that was placed last was shown first.

What has caused this to reverse the order? What can I do or not do to make sure that the correct order in which I have placed the slides is preserved?

Thanks for your help.