I'm working on a model of the space shuttle and built an articulated arm to be animated in a seperate file and imported it into the main scene. I parented it to the shuttle and animated it. Then I rendered a quicktime animation. I then closed the scene after saving it. When I re-opened the scene I got this message: "An object description is missing in the file. Do you wish to continue? (a cube will replace the missing object)" Sure enough, a part of the arm had become a cube. This fortunately, is not a big problem because I still have the original files and can set up the simple animation with no problem but I'm a little worried that it will happen again. I am on a Windows machine if that's any help.