iPhoto Slideshow Crashing

New to Apples and struggling with iPhoto. Love it so far with just one problem. When I chose to view photos via Slideshow it works fine for a while, say 30 to 40 photos, then freezes. Are there limits to the number of photos that can work with Slideshow? I have traveled a lot and have a lot of photos in groups, some groups with over 500 shots. Am I overloading the program? It gives me a rather nondescript error telling me that it has stopped but not why. The first time it happened the entire computer froze and I had to Force Quit.

I have a new computer, the 27 inch desktop, had it for around a month.
Any ideas?

Thanks.