Quoting Mandy and her girls!~:" Not sure if anyone can help me since this is more computer related but I have a mac and whenever I open ... [snip!] ... the app my screen goes back to normal. It's never done this before and I did not change any settings. Very frustrating haha."
Okay, now I don't use a Mac but just knowing what I know about computers I'd say:
1) Straight software issue with iphoto, you should uninstall and reinstall the program.
2) Video driver issue. Generally your computer doesn't need as many video/graphics resources when you're just puttering around, but when you need to use an image editing software it can kick it into high gear and you can see problems you might not see otherwise. You could try installing another photo editing software and see if you get a similar result. If you do, you might need to uninstall and reinstall the driver.. but not sure how that works on a Mac.
3) Actual graphics hardware issue - similar reasoning as above.
Again.. I am not really a Mac person, I can use one but I have never tried to repair one lol. Good luck.