keynote crashes

Hi,

I'm using a brand new MacBook Air with a 4 GB memory and 1.8 GHz Intel Core i7 processor - running Lion - and I'm using Keynote - and I'm getting continual crashes. The file size was originally around 140 MB, heavy with grapihics and movies, so I compressed it too around 75MB- but it still crashes when I try to change +add new images. Occasionally when it goes down it will replace certain images with grey boxes with question marks in. Any ideas folk?

Julian of Sweden