After some questions we've received on problems with iPhoto John Carter sends this advice, "This could be an indication that the hard drive in the computer is starting to fail, or that you are running out of space on your internal hard drive.
"First, check to see how much space is left on the hard drive. If you have at less than 1GB of free space, I would be concerned. A small amount of available space on the internal hard drive clearly indicates that you need an external hard drive and need to move folders from the internal hard drive to the external hard drive to give the Mac room to work in.
"Check the internal hard drive available space by right-clicking on the 'Macintosh HD' in the 'Devices' section of the Finder, then clicking on 'Get Info.'
The popup should look something like this.
"To help in isolating the problem, you could add a second, external hard drive anyway and move your iPhoto library to that hard drive. This is not a straightforward operation, so it is best done by someone who knows what they are doing. By moving the iPhoto library to a new external hard drive, if the problem persists then you will know it has something to do with either the Mac, the iPhoto application, or the way you are accessing or manipulating the photos.
"Having an external hard drive for your iPhoto library could actually speed things up when accessing iPhoto since your iPhoto library is quite large. The technical explanation for this is complicated. I have found that there is an initial time lag when accessing my external hard drives, but only when they have 'gone to sleep,' which is normal. If the external hard drives are active, then everything works fast. I use an external hard drive for all my videos and many of my photos.
"You could also have someone sit with you while you work with iPhoto to see if they can catch what might be causing the problem, but that could take hours to wait for the problem to show up, and this is why I think moving the iPhoto library to an external hard drive would be a better way to approach the problem."