Captivate has never been backwards compatible, and that has not changed: you can open a CP5 file in CP6 but once you save it, file we be converted to the new format and you will not be able to open it again in CP5
Thanks Lilybiri. Can I then open the Captivate 5 in Captivate 6 and cool "captivate 6" features to it? I know I would then have to save it as a Captivate 6 file and I could then no longer edit it with Captivate 5.