Just to let you know, in P4 I've had a number of files (with numerous figures posed) become corrupted where a previously saved file is opened and the figures are listed in the drop down menu but are not on the screen. They were on the screen when I saved the file, but are now invisible. No amount of Show All, Hierarchy checking, arrowing up, or double clicking helped. I just had to start over. I could never predict, force, or track the problem. It was just an unwelcome surprise. My suggestion is never save over a previously saved file. Just save new versions. When your hard drive becomes full or slows down too much, judiciously delete older versions.