My dad has a new 27" Core i5 iMac. When he plays a very long slideshow, iPhoto consistently crashes around the 8-minute mark. Sometimes he gets an error message saying "iPhoto unexpectedly quit" and sometimes the slides just quit coming up, even though the music keeps playing. It doesn't matter from which event the slides come, although it seems to happen on his pics only and not on the pre-installed pics from Apple. One last data point, this never happens, even when viewing the same slideshow, on his 13" MacBook Pro, which he bought at the same time. It seems to me like a memory leak, or, less likely, some kind of GPU overheating issue. He's tried rebuilding his photo library, which changed nothing. Apple tech support has been useless. Hypothesis?