I had this problem when I had only the 256mb RAM it came pre-installed with. It seemed to be getting progressively slower. I found upgrading it to 768mb of RAM was a massive boost in speed and apps opened a LOT faster. iPhoto was one of the apps that opened a lot quicker. Now I have a gig of ram, but the extra RAM from 768mb hardly ever gets used... I would recommend getting more RAM. 🙂