iMovie on iPhone4 render issue

Im on holiday and have almost exclusively used my iPhone to record pictures and movies of our family holiday and then create a story of our holiday with iMovie on the iPhone. I must say it is fantastic and well done Apple and the development team a great success.
The video I have created is a combination of iPhone taken videos and still images. The current movie is approximately 4 minutes in length.
I have found (and I dont know if its a size thing?) that the still images and video is no longer rendered such that I can not preview what I have. If I Play the video I get a black screen. So the only way I can really see what Ive got is to export the video (i.e. do a complete render).
Id love to know whats going on or perhaps whats broken?
One other challenge Ive faced and need to work on solving is... we were out on the water one day and I deliberately left the iPhone back in the hotel (I wasnt loosing that overboard). So I took the Lumix TZ7 with me instead. Guess who now wants to get those images and the video back onto the iPhone to incorporate into the video! - Im sure this is possible even if there are some hoops to jump through.
Apple - a great experience. Looking forward to seeing the movie on AppleTV when I get home.
David
MacBook Pro 2.66 GHz Intel i7 iOS 4 iPhone Develope