I just got this program and did a whole layout but when I went to save it as a PNG file it won't let me save it in that format. I want to be able to save it so I can work on it later but not have it flatten and not be able to make changes. Am I missing something?? Do I have to have a special program to be able to save in that format? The program just shut down on me and I lost my whole layout! So frustrating!!